A transferase is any one of a class of
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s that catalyse the transfer of specific
functional group
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest ...
s (e.g. a
methyl
In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...
or
glycosyl
A glycosyl group is a univalent free radical or substituent structure obtained by removing the hemiacetal hydroxyl group from the cyclic form of a monosaccharide and, by extension, of a lower oligosaccharide.
Glycosyl also reacts with inorganic a ...
group) from one
molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
(called the donor) to another (called the acceptor). They are involved in hundreds of different
biochemical pathways
In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical reac ...
throughout biology, and are integral to some of life's most important processes.
Transferases are involved in myriad reactions in the cell. Three examples of these reactions are the activity of
coenzyme A
Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All genomes sequenced to date encode enzymes that use coenzyme A as a subs ...
(CoA)
transferase
A transferase is any one of a class of enzymes that catalyse the transfer of specific functional groups (e.g. a methyl or glycosyl group) from one molecule (called the donor) to another (called the acceptor). They are involved in hundreds of di ...
, which transfers
thiol esters,
the action of
N-acetyltransferase N-acetyltransferase (NAT) is an enzyme that catalyzes the transfer of acetyl groups from acetyl-CoA to arylamines, arylhydroxylamines and arylhydrazines. They have wide specificity for aromatic amines, particularly serotonin, and can also catal ...
, which is part of the pathway that metabolizes
tryptophan
Tryptophan (symbol Trp or W)
is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α- carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...
, and the regulation of
pyruvate dehydrogenase
Pyruvate dehydrogenase is an enzyme that catalyzes the reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide. The conversion requires the coenzyme thiamine pyrophosphate.
Pyruvate dehydrogenase is us ...
(PDH), which converts
pyruvate
Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell.
Pyruvic aci ...
to
acetyl CoA
Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for ...
. Transferases are also utilized during translation. In this case, an amino acid chain is the functional group transferred by a
peptidyl transferase
The peptidyl transferase is an aminoacyltransferase () as well as the primary enzymatic function of the ribosome, which forms peptide bonds between adjacent amino acids using tRNAs during the translation process of protein biosynthesis. The subs ...
. The transfer involves the removal of the growing
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
chain from the
tRNA
Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino ac ...
molecule in the
A-site
The A-site (A for aminoacyl) of a ribosome is a binding site for charged t-RNA molecules during protein synthesis. One of three such binding sites, the A-site is the first location the t-RNA binds during the protein synthesis process, the other t ...
of the
ribosome
Ribosomes ( ) are macromolecular machines, found within all cells, that perform biological protein synthesis (mRNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA (mRNA) molecules to ...
and its subsequent addition to the amino acid attached to the tRNA in the
P-site The P-site (for peptidyl) is the second binding site for tRNA in the ribosome. The other two sites are the A-site (aminoacyl), which is the first binding site in the ribosome, and the E-site (exit), the third. During protein translation, the P-site ...
.
Mechanistically, an enzyme that catalyzed the following reaction would be a transferase:
In the above reaction, X would be the donor, and Y would be the acceptor. "Group" would be the functional group transferred as a result of transferase activity. The donor is often a
coenzyme
A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's role as a catalyst (a catalyst is a substance that increases the rate of a chemical reaction). Cofactors can be considered "helper molecules" that ass ...
.
History
Some of the most important discoveries relating to transferases occurred as early as the 1930s. Earliest discoveries of transferase activity occurred in other classifications of
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s, including
beta-galactosidase
β-Galactosidase (EC 3.2.1.23, lactase, beta-gal or β-gal; systematic name β-D-galactoside galactohydrolase), is a glycoside hydrolase enzyme that catalyzes hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides.
β- ...
,
protease
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
, and acid/base
phosphatase
In biochemistry, a phosphatase is an enzyme that uses water to cleave a phosphoric acid Ester, monoester into a phosphate ion and an Alcohol (chemistry), alcohol. Because a phosphatase enzyme catalysis, catalyzes the hydrolysis of its Substrate ...
. Prior to the realization that individual enzymes were capable of such a task, it was believed that two or more enzymes enacted functional group transfers.
Transamination
Transamination is a chemical reaction that transfers an amino group to a ketoacid to form new amino acids. This pathway is responsible for the deamination of most amino acids. This is one of the major degradation pathways which convert essential a ...
, or the transfer of an
amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...
(or NH
2) group from an amino acid to a
keto acid
In organic chemistry, keto acids or ketoacids (also called oxo acids or oxoacids) are organic compounds that contain a carboxylic acid group () and a ketone group ().Franz Dietrich Klingler, Wolfgang Ebertz "Oxocarboxylic Acids" in Ullmann's E ...
by an
aminotransferase
Transaminases or aminotransferases are enzymes that catalyze a transamination reaction between an amino acid and an α-keto acid. They are important in the synthesis of amino acids, which form proteins.
Function and mechanism
An amino acid co ...
(also known as a "transaminase"), was first noted in 1930 by
Dorothy M. Needham, after observing the disappearance of
glutamic acid
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synt ...
added to pigeon breast muscle. This observance was later verified by the discovery of its reaction mechanism by Braunstein and Kritzmann in 1937. Their analysis showed that this reversible reaction could be applied to other tissues. This assertion was validated by
Rudolf Schoenheimer's work with
radioisotope
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
s as
tracers
Tracer may refer to:
Science
* Flow tracer, any fluid property used to track fluid motion
* Fluorescent tracer, a substance such as 2-NBDG containing a fluorophore that is used for tracking purposes
* Histochemical tracer, a substance used for tr ...
in 1937.
This in turn would pave the way for the possibility that similar transfers were a primary means of producing most amino acids via amino transfer.
Another such example of early transferase research and later reclassification involved the discovery of uridyl transferase. In 1953, the enzyme
UDP-glucose pyrophosphorylase
Uridine diphosphate glucose (uracil-diphosphate glucose, UDP-glucose) is a nucleotide sugar. It is involved in glycosyltransferase reactions in metabolism.
Functions
UDP-glucose is used in nucleotide sugar metabolism as an activated form of glu ...
was shown to be a transferase, when it was found that it could reversibly produce
UTP and
G1P from
UDP-glucose
Uridine diphosphate glucose (uracil-diphosphate glucose, UDP-glucose) is a nucleotide sugar. It is involved in glycosyltransferase reactions in metabolism.
Functions
UDP-glucose is used in nucleotide sugar metabolism as an activated form of glu ...
and an organic
pyrophosphate
In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P–O–P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate (Na2H2P2O7) and tetrasodium pyrophosphate (Na4P2O7), among other ...
.
Another example of historical significance relating to transferase is the discovery of the mechanism of
catecholamine
A catecholamine (; abbreviated CA) is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine.
Catechol can be either a free molecule or a subst ...
breakdown by
catechol-O-methyltransferase
Catechol-''O''-methyltransferase (COMT; ) is one of several enzymes that degrade catecholamines (neurotransmitters such as dopamine, epinephrine, and norepinephrine), catecholestrogens, and various drugs and substances having a catechol struct ...
. This discovery was a large part of the reason for
Julius Axelrod
Julius Axelrod (May 30, 1912 – December 29, 2004) was an American biochemist. He won a share of the Nobel Prize in Physiology or Medicine in 1970 along with Bernard Katz and Ulf von Euler. The Nobel Committee honored him for his work on the re ...
’s 1970
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...
(shared with
Sir Bernard Katz
Sir Bernard Katz, FRS (; 26 March 1911 – 20 April 2003) was a German-born British physician and biophysicist, noted for his work on nerve physiology. He shared the Nobel Prize in physiology or medicine in 1970 with Julius Axelrod and Ulf von ...
and
Ulf von Euler
Ulf Svante von Euler (7 February 1905 – 9 March 1983) was a Swedish physiologist and pharmacologist. He shared the Nobel Prize in Physiology or Medicine in 1970 for his work on neurotransmitters.
Life
Ulf Svante von Euler-Chelpin was born in ...
).
Classification of transferases continues to this day, with new ones being discovered frequently. An example of this is Pipe, a sulfotransferase involved in the dorsal-ventral patterning of ''
Drosophila
''Drosophila'' () is a genus of flies, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species ...
''. Initially, the exact mechanism of Pipe was unknown, due to a lack of information on its substrate. Research into Pipe's catalytic activity eliminated the likelihood of it being a heparan sulfate glycosaminoglycan. Further research has shown that Pipe targets the ovarian structures for sulfation. Pipe is currently classified as a ''Drosophila''
heparan sulfate 2-O-sulfotransferase.
Nomenclature
Systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature.
A semisystematic name or semitrivial ...
s of transferases are constructed in the form of "donor:acceptor grouptransferase."
For example, methylamine:L-glutamate N-methyltransferase would be the standard naming convention for the transferase
methylamine-glutamate N-methyltransferase, where
methylamine
Methylamine is an organic compound with a formula of . This colorless gas is a derivative of ammonia, but with one hydrogen atom being replaced by a methyl group. It is the simplest primary amine.
Methylamine is sold as a solution in methanol, ...
is the donor,
L-glutamate
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synt ...
is the acceptor, and
methyltransferase
Methyltransferases are a large group of enzymes that all methylate their substrates but can be split into several subclasses based on their structural features. The most common class of methyltransferases is class I, all of which contain a Ross ...
is the EC category grouping. This same action by the transferase can be illustrated as follows:
:methylamine + L-glutamate
NH3 +
N-methyl-L-glutamate
However, other accepted names are more frequently used for transferases, and are often formed as "acceptor grouptransferase" or "donor grouptransferase." For example, a
DNA methyltransferase
In biochemistry, the DNA methyltransferase (DNA MTase, DNMT) family of enzymes catalyze the transfer of a methyl group to DNA. DNA methylation serves a wide variety of biological functions. All the known DNA methyltransferases use S-adenosyl m ...
is a transferase that catalyzes the transfer of a
methyl
In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...
group to a
DNA acceptor. In practice, many molecules are not referred to using this terminology due to more prevalent common names. For example,
RNA polymerase
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template.
Using the enzyme helicase, RNAP locally opens the ...
is the modern common name for what was formerly known as RNA nucleotidyltransferase, a kind of
nucleotidyl transferase that transfers
nucleotides
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules w ...
to the 3’ end of a growing
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
strand. In the EC system of classification, the accepted name for RNA polymerase is DNA-directed RNA polymerase.
Classification
Described primarily based on the type of biochemical group transferred, transferases can be divided into ten categories (based on the
EC Number classification).
These categories comprise over 450 different unique enzymes.
In the EC numbering system, transferases have been given a classification of EC2.
Hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...
is not considered a functional group when it comes to transferase targets; instead, hydrogen transfer is included under
oxidoreductase
In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This group of enzymes usually ut ...
s,
[ due to electron transfer considerations.
]
Role
EC 2.1: single carbon transferases
EC 2.1 includes enzymes that transfer single-carbon groups. This category consists of transfers of methyl
In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...
, hydroxymethyl
The hydroxymethyl group is the name for a substituent with the structural formula −CH2−OH. It consists of a methylene bridge (−CH2− unit) bonded to a hydroxyl group (−OH). This makes the hydroxymethyl group an alcohol. It has the identic ...
, formyl, carboxy, carbamoyl
Carbamic acid, which might also be called aminoformic acid or aminocarboxylic acid, is the chemical compound with the formula . It can be obtained by the reaction of ammonia and carbon dioxide at very low temperatures, which also yields an equ ...
, and amido groups. Carbamoyltransferases, as an example, transfer a carbamoyl group from one molecule to another. Carbamoyl groups follow the formula NH2CO. In ATCase such a transfer is written as carbamoyl phosphate
Carbamoyl phosphate is an anion of biochemical significance. In land-dwelling animals, it is an intermediary metabolite in nitrogen disposal through the urea cycle and the synthesis of pyrimidines. Its enzymatic counterpart, carbamoyl phosphate syn ...
+ L-aspartate
Aspartic acid (symbol Asp or D; the ionic form is known as aspartate), is an α-amino acid that is used in the biosynthesis of proteins. Like all other amino acids, it contains an amino group and a carboxylic acid. Its α-amino group is in the pro ...
L-carbamoyl aspartate + phosphate
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid .
The phosphate or orthophosphate ion is derived from phospho ...
.
EC 2.2: aldehyde and ketone transferases
Enzymes that transfer aldehyde or ketone groups and included in EC 2.2. This category consists of various transketolases and transaldolases. Transaldolase, the namesake of aldehyde transferases, is an important part of the pentose phosphate pathway. The reaction it catalyzes consists of a transfer of a dihydroxyacetone functional group to glyceraldehyde 3-phosphate
Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is a metabolite that occurs as an intermediate in several central pathways of all organisms.Nelson, D ...
(also known as G3P). The reaction is as follows: sedoheptulose 7-phosphate
Sedoheptulose 7-phosphate is an intermediate in the pentose phosphate pathway.
It is formed by transketolase and acted upon by transaldolase.
Sedoheptulokinase is an enzyme that uses sedoheptulose and ATP to produce ADP and sedoheptulose 7-phosp ...
+ glyceraldehyde 3-phosphate erythrose 4-phosphate
Erythrose 4-phosphate is a phosphate of the simple sugar erythrose. It is an intermediate in the pentose phosphate pathway and the Calvin cycle.
In addition, it serves as a precursor in the biosynthesis of the aromatic amino acids tyrosine, pheny ...
+ fructose 6-phosphate
Fructose 6-phosphate (sometimes called the Neuberg ester) is a derivative of fructose, which has been phosphorylated at the 6-hydroxy group. It is one of several possible fructosephosphates. The β-D-form of this compound is very common in cells. ...
.
EC 2.3: acyl transferases
Transfer of acyl groups or acyl groups that become alkyl groups during the process of being transferred are key aspects of EC 2.3. Further, this category also differentiates between amino-acyl and non-amino-acyl groups. Peptidyl transferase
The peptidyl transferase is an aminoacyltransferase () as well as the primary enzymatic function of the ribosome, which forms peptide bonds between adjacent amino acids using tRNAs during the translation process of protein biosynthesis. The subs ...
is a ribozyme
Ribozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of protein enzymes. The 1982 discovery of ribozymes demonst ...
that facilitates formation of peptide bonds
In organic chemistry, a peptide bond is an amide type of covalent chemical bond linking two consecutive alpha-amino acids from C1 (carbon number one) of one alpha-amino acid and N2 (nitrogen number two) of another, along a peptide or protein cha ...
during translation
Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...
. As an aminoacyltransferase, it catalyzes the transfer of a peptide to an aminoacyl-tRNA
Aminoacyl-tRNA (also aa-tRNA or charged tRNA) is tRNA to which its cognate amino acid is chemically bonded (charged). The aa-tRNA, along with particular elongation factors, deliver the amino acid to the ribosome for incorporation into the polypept ...
, following this reaction: peptidyl-tRNAA + aminoacyl-tRNAB tRNAA + peptidyl aminoacyl-tRNAB.
EC 2.4: glycosyl, hexosyl, and pentosyl transferases
EC 2.4 includes enzymes that transfer glycosyl
A glycosyl group is a univalent free radical or substituent structure obtained by removing the hemiacetal hydroxyl group from the cyclic form of a monosaccharide and, by extension, of a lower oligosaccharide.
Glycosyl also reacts with inorganic a ...
groups, as well as those that transfer hexose and pentose. Glycosyltransferase
Glycosyltransferases (GTFs, Gtfs) are enzymes ( EC 2.4) that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the "glycosyl donor") to a nucleophilic glycos ...
is a subcategory of EC 2.4 transferases that is involved in biosynthesis
Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. ...
of disaccharides
A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, lac ...
and polysaccharides
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with w ...
through transfer of monosaccharides
Monosaccharides (from Greek ''monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built.
They are usually colorless, water-solu ...
to other molecules. An example of a prominent glycosyltransferase is lactose synthase
Lactose synthase is an enzyme that generates lactose from glucose and UDP-galactose.
It is classified under .
It consists of N-acetyllactosamine synthase and alpha-lactalbumin. Alpha-lactalbumin, which is expressed in response to prolactin
...
which is a dimer possessing two protein subunit
In structural biology, a protein subunit is a polypeptide chain or single protein molecule that assembles (or "''coassembles''") with others to form a protein complex.
Large assemblies of proteins such as viruses often use a small number of ty ...
s. Its primary action is to produce lactose
Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffix '' - ...
from glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
and UDP-galactose. This occurs via the following pathway: UDP-β-D-galactose + D-glucose UDP + lactose.
EC 2.5: alkyl and aryl transferases
EC 2.5 relates to enzymes that transfer alkyl or aryl groups, but does not include methyl groups. This is in contrast to functional groups that become alkyl groups when transferred, as those are included in EC 2.3. EC 2.5 currently only possesses one sub-class: Alkyl and aryl transferases. Cysteine synthase, for example, catalyzes the formation of acetic acids and cysteine
Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile.
When present as a deprotonated catalytic residue, sometime ...
from O3-acetyl-L-serine and hydrogen sulfide: O3-acetyl-L-serine + H2S L-cysteine + acetate.
EC 2.6: nitrogenous transferases
The grouping consistent with transfer of nitrogenous
Nitrogen is the chemical element with the Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the pnictogens. It is a common element in the ...
groups is EC 2.6. This includes enzymes like transaminase
Transaminases or aminotransferases are enzymes that catalyze a transamination reaction between an amino acid and an α-keto acid. They are important in the synthesis of amino acids, which form proteins.
Function and mechanism
An amino acid co ...
(also known as "aminotransferase"), and a very small number of oximinotransferase
In enzymology, an oximinotransferase () is an enzyme that catalyzes the chemical reaction
:pyruvate oxime + acetone \rightleftharpoons pyruvate + acetone oxime
Thus, the two substrates of this enzyme are pyruvate oxime and acetone, whereas it ...
s and other nitrogen group transferring enzymes. EC 2.6 previously included amidinotransferase but it has since been reclassified as a subcategory of EC 2.1 (single-carbon transferring enzymes). In the case of aspartate transaminase
Aspartate transaminase (AST) or aspartate aminotransferase, also known as AspAT/ASAT/AAT or (serum) glutamic oxaloacetic transaminase (GOT, SGOT), is a pyridoxal phosphate (PLP)-dependent transaminase enzyme () that was first described by Arthur ...
, which can act on tyrosine
-Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...
, phenylalanine
Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino a ...
, and tryptophan
Tryptophan (symbol Trp or W)
is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α- carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...
, it reversibly transfers an amino
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent s ...
group from one molecule to the other.
The reaction, for example, follows the following order: L-aspartate +2-oxoglutarate oxaloacetate + L-glutamate.
EC 2.7: phosphorus transferases
While EC 2.7 includes enzymes that transfer phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
-containing groups, it also includes nuclotidyl transferases as well. Sub-category phosphotransferase
Phosphotransferases are a category of enzymes ( EC number 2.7) that catalyze phosphorylation reactions. The general form of the reactions they catalyze is:
:A-P + B \rightleftharpoons B-P + A
Where ''P'' is a phosphate group and A and B are the do ...
is divided up in categories based on the type of group that accepts the transfer. Groups that are classified as phosphate acceptors include: alcohols, carboxy groups, nitrogenous groups, and phosphate groups. Further constituents of this subclass of transferases are various kinases. A prominent kinase is cyclin-dependent kinase
Cyclin-dependent kinases (CDKs) are the families of protein kinases first discovered for their role in regulating the cell cycle. They are also involved in regulating transcription, mRNA processing, and the differentiation of nerve cells. They a ...
(or CDK), which comprises a sub-family of protein kinase
A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them (phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a fu ...
s. As their name implies, CDKs are heavily dependent on specific cyclin molecules for activation
Activation, in chemistry and biology, is the process whereby something is prepared or excited for a subsequent reaction.
Chemistry
In chemistry, "activation" refers to the reversible transition of a molecule into a nearly identical chemical or ...
. Once combined, the CDK-cyclin complex is capable of enacting its function within the cell cycle.
The reaction catalyzed by CDK is as follows: ATP + a target protein ADP + a phosphoprotein.
EC 2.8: sulfur transferases
Transfer of sulfur-containing groups is covered by EC 2.8 and is subdivided into the subcategories of sulfurtransferases, sulfotransferases, and CoA-transferases, as well as enzymes that transfer alkylthio groups. A specific group of sulfotransferases are those that use PAPS as a sulfate group donor. Within this group is alcohol sulfotransferase which has a broad targeting capacity. Due to this, alcohol sulfotransferase is also known by several other names including "hydroxysteroid sulfotransferase," "steroid sulfokinase," and "estrogen sulfotransferase." Decreases in its activity has been linked to human liver disease. This transferase acts via the following reaction: 3'-phosphoadenylyl sulfate + an alcohol adenosine 3',5'bisphosphate + an alkyl sulfate.
EC 2.9: selenium transferases
EC 2.9 includes enzymes that transfer selenium
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, ...
-containing groups. This category only contains two transferases, and thus is one of the smallest categories of transferase. Selenocysteine synthase, which was first added to the classification system in 1999, converts seryl-tRNA(Sec UCA) into selenocysteyl-tRNA(Sec UCA).
EC 2.10: metal transferases
The category of EC 2.10 includes enzymes that transfer molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...
or tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolat ...
-containing groups. However, as of 2011, only one enzyme has been added: molybdopterin molybdotransferase
Molybdopterin molybdotransferase (, ''MoeA'', ''Cnx1'') is an enzyme with systematic name ''adenylyl-molybdopterin:molybdate molybdate transferase (AMP-forming)''. This enzyme catalyses the following chemical reaction
: adenylyl-molybdopterin + m ...
. This enzyme is a component of MoCo biosynthesis in ''Escherichia coli''. The reaction it catalyzes is as follows: adenylyl-molybdopterin
Molybdopterins are a class of cofactors found in most molybdenum-containing and all tungsten-containing enzymes. Synonyms for molybdopterin are: MPT and pyranopterin-dithiolate. The nomenclature for this biomolecule can be confusing: Molybdopter ...
+ molybdate
In chemistry a molybdate is a compound containing an oxoanion with molybdenum in its highest oxidation state of 6. Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended structures, althou ...
molybdenum cofactor + AMP.
Role in histo-blood group
The A and B transferases are the foundation of the human ABO blood group system. Both A and B transferases are glycosyltransferases, meaning they transfer a sugar molecule onto an H-antigen. This allows H-antigen to synthesize the glycoprotein
Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...
and glycolipid
Glycolipids are lipids with a carbohydrate attached by a glycosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connec ...
conjugates that are known as the A/B antigens
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...
. The full name of A transferase is alpha 1-3-N-acetylgalactosaminyltransferase and its function in the cell is to add N-acetylgalactosamine to H-antigen, creating A-antigen. The full name of B transferase is alpha 1-3-galactosyltransferase, and its function in the cell is to add a galactose
Galactose (, '' galacto-'' + '' -ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molec ...
molecule to H-antigen, creating B-antigen.
It is possible for ''Homo sapiens
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
'' to have any of four different blood type
A blood type (also known as a blood group) is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrate ...
s: Type A (express A antigens), Type B (express B antigens), Type AB (express both A and B antigens) and Type O (express neither A nor B antigens). The gene for A and B transferases is located on chromosome 9
Chromosome 9 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome, as they normally do with all chromosomes. Chromosome 9 spans about 138 million base pairs of nucleic acids (the building blocks of D ...
. The gene contains seven exon
An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequen ...
s and six intron
An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e. a region inside a gene."The notion of the cistron .e., gene. ...
s and the gene itself is over 18kb long. The alleles for A and B transferases are extremely similar. The resulting enzymes only differ in 4 amino acid residues. The differing residues are located at positions 176, 235, 266, and 268 in the enzymes.
Deficiencies
.
Transferase deficiencies are at the root of many common illness
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that ar ...
es. The most common result of a transferase deficiency is a buildup of a cellular product.
SCOT deficiency
Succinyl-CoA:3-ketoacid CoA transferase deficiency (or SCOT deficiency) leads to a buildup of ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s.
Ketones
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...
are created upon the breakdown of fats in the body and are an important energy source. Inability to utilize ketones
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...
leads to intermittent ketoacidosis
Ketoacidosis is a metabolic state caused by uncontrolled production of ketone bodies that cause a metabolic acidosis. While ketosis refers to any elevation of blood ketones, ketoacidosis is a specific pathologic condition that results in changes ...
, which usually first manifests during infancy. Disease sufferers experience nausea, vomiting, inability to feed, and breathing difficulties. In extreme cases, ketoacidosis can lead to coma and death. The deficiency is caused by mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mi ...
in the gene OXCT1. Treatments mostly rely on controlling the diet of the patient.
CPT-II deficiency
Carnitine palmitoyltransferase II
Carnitine O-palmitoyltransferase 2, mitochondrial is an enzyme that in humans is encoded by the ''CPT2'' gene.
Function
Carnitine palmitoyltransferase II precursor (CPT2) is a mitochondrial membrane protein which is transported to the mitochon ...
deficiency (also known as CPT-II deficiency) leads to an excess long chain fatty acids
In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
, as the body
Body may refer to:
In science
* Physical body, an object in physics that represents a large amount, has mass or takes up space
* Body (biology), the physical material of an organism
* Body plan, the physical features shared by a group of anima ...
lacks the ability to transport fatty acids into the mitochondria
A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...
to be processed as a fuel source. The disease is caused by a defect in the gene CPT2. This deficiency will present in patients in one of three ways: lethal neonatal, severe infantile hepatocardiomuscular, and myopathic form. The myopathic is the least severe form of the deficiency and can manifest at any point in the lifespan of the patient. The other two forms appear in infancy. Common symptoms of the lethal neonatal form and the severe infantile forms are liver failure, heart problems, seizures and death. The myopathic form is characterized by muscle pain and weakness following vigorous exercise. Treatment generally includes dietary modifications and carnitine supplements.
Galactosemia
Galactosemia
Galactosemia (British galactosaemia, from Greek γαλακτόζη + αίμα, meaning galactose + blood, accumulation of galactose in blood) is a rare genetic metabolic disorder that affects an individual's ability to metabolize the sugar galacto ...
results from an inability to process galactose, a simple sugar
Monosaccharides (from Greek ''monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built.
They are usually colorless, water-solub ...
. This deficiency occurs when the gene for galactose-1-phosphate uridylyltransferase
Galactose-1-phosphate uridylyltransferase (or GALT, G1PUT) is an enzyme () responsible for converting ingested galactose to glucose.
Galactose-1-phosphate uridylyltransferase (GALT) catalyzes the second step of the Leloir pathway of galactose ...
(GALT) has any number of mutations, leading to a deficiency in the amount of GALT produced. There are two forms of Galactosemia: classic and Duarte. Duarte galactosemia
Duarte galactosemia is an inherited condition associated with diminished ability to metabolize galactose due to a partial deficiency of the enzyme galactose-1-phosphate uridylyltransferase.Fridovich-Keil, J., et al., Duarte Variant Galactosemia, ...
is generally less severe than classic galactosemia and is caused by a deficiency of galactokinase
Galactokinase is an enzyme (phosphotransferase) that facilitates the phosphorylation of α-D-galactose to galactose 1-phosphate at the expense of one molecule of ATP. Galactokinase catalyzes the second step of the Leloir pathway, a metabolic ...
. Galactosemia renders infants unable to process the sugars in breast milk, which leads to vomiting and anorexia
Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...
within days of birth. Most symptoms of the disease are caused by a buildup of galactose-1-phosphate
D-Galactose-1-phosphate is an intermediate in the intraconversion of glucose and uridine diphosphate galactose. It is formed from galactose by galactokinase.The improper metabolism of galactose-1-phosphate is a characteristic of galactosemia. The L ...
in the body. Common symptoms include liver failure, sepsis
Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
, failure to grow, and mental impairment, among others. Buildup of a second toxic substance, galactitol
Galactitol (dulcitol) is a sugar alcohol, the reduction product of galactose. It has a slightly sweet taste. In people with galactokinase deficiency, a form of galactosemia, excess dulcitol forms in the lens of the eye leading to cataracts.
Gala ...
, occurs in the lenses of the eyes, causing cataract
A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
s. Currently, the only available treatment is early diagnosis followed by adherence to a diet devoid of lactose, and prescription of antibiotics for infections that may develop.
Choline acetyltransferase deficiencies
Choline acetyltransferase (also known as ChAT or CAT) is an important enzyme which produces the neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell.
Neuro ...
acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...
. Acetylcholine is involved in many neuropsychic functions such as memory, attention, sleep and arousal.
The enzyme is globular in shape and consists of a single amino acid chain. ChAT functions to transfer an acetyl group from acetyl co-enzyme A to choline Choline is an essential nutrient for humans and many other animals. Choline occurs as a cation that forms various salts (X− in the depicted formula is an undefined counteranion). Humans are capable of some ''de novo synthesis'' of choline but re ...
in the synapse
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses from ...
s of nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
cells and exists in two forms: soluble and membrane bound. The ChAT gene is located on chromosome 10
Chromosome 10 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 10 spans about 133 million base pairs (the building material of DNA) and represents between 4 and 4.5 percent of the tot ...
.
Alzheimer's disease
Decreased expression of ChAT is one of the hallmarks of Alzheimer's disease
Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...
. Patients with Alzheimer's disease show a 30 to 90% reduction in activity in several regions of the brain, including the temporal lobe
The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The temporal lobe ...
, the parietal lobe
The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus.
The parietal lobe integrates sensory informa ...
and the frontal lobe
The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove betwe ...
. However, ChAT deficiency is not believed to be the main cause of this disease.
Amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease)
Patients with ALS
Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or Lou Gehrig's disease, is a neurodegenerative disease that results in the progressive loss of motor neurons that control voluntary muscles. ALS is the most com ...
show a marked decrease in ChAT activity in motor neurons in the spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...
and brain
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
. Low levels of ChAT activity are an early indication of the disease and are detectable long before motor neurons begin to die. This can even be detected before the patient is symptomatic
Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showi ...
.
Huntington's disease
Patients with Huntington's also show a marked decrease in ChAT production. Though the specific cause of the reduced production is not clear, it is believed that the death of medium-sized motor neurons with spiny dendrite
Dendrites (from Greek δένδρον ''déndron'', "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the n ...
s leads to the lower levels of ChAT production.
Schizophrenia
Patients with Schizophrenia also exhibit decreased levels of ChAT, localized to the mesopontine tegment of the brain and the nucleus accumbens
The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for "nucleus adjacent to the septum") is a region in the basal forebrain rostral to the preoptic area of the hypotha ...
, which is believed to correlate with the decreased cognitive functioning experienced by these patients.
Sudden infant death syndrome (SIDS)
Recent studies have shown that SIDS
Sudden infant death syndrome (SIDS) is the sudden unexplained death of a child of less than one year of age. Diagnosis requires that the death remain unexplained even after a thorough autopsy and detailed death scene investigation. SIDS usual ...
infants show decreased levels of ChAT in both the hypothalamus
The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...
and the striatum
The striatum, or corpus striatum (also called the striate nucleus), is a nucleus (a cluster of neurons) in the subcortical basal ganglia of the forebrain. The striatum is a critical component of the motor and reward systems; receives glutamate ...
. SIDS infants also display fewer neurons capable of producing ChAT in the vagus system. These defects in the medulla could lead to an inability to control essential autonomic functions such as the cardiovascular
The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
and respiratory
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
systems.
Congenital myasthenic syndrome (CMS)
CMS
CMS may refer to:
Computing
* Call management system
* CMS-2 (programming language), used by the United States Navy
* Code Morphing Software, a technology used by Transmeta
* Collection management system for a museum collection
* Color manag ...
is a family of diseases that are characterized by defects in neuromuscular transmission which leads to recurrent bouts of apnea
Apnea, BrE: apnoea, is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are ( patency), there ...
(inability to breathe) that can be fatal. ChAT deficiency is implicated in myasthenia syndromes where the transition problem occurs presynaptic
In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential to the transmission of nervous impulses from ...
ally. These syndromes are characterized by the patients’ inability to resynthesize acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...
.
Uses in biotechnology
Terminal transferases
Terminal transferases are transferases that can be used to label DNA or to produce plasmid vector
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; how ...
s. It accomplishes both of these tasks by adding deoxynucleotides in the form of a template to the downstream
Downstream may refer to:
* Downstream (bioprocess)
* Downstream (manufacturing)
* Downstream (networking)
* Downstream (software development)
* Downstream (petroleum industry)
* Upstream and downstream (DNA), determining relative positions on DNA ...
end or 3' end of an existing DNA molecule.
Terminal transferase is one of the few DNA polymerases that can function without an RNA primer.
Glutathione transferases
The family of glutathione transferases (GST) is extremely diverse, and therefore can be used for a number of biotechnological purposes. Plants use glutathione transferases as a means to segregate toxic metals from the rest of the cell. These glutathione transferases can be used to create biosensor
A biosensor is an analytical device, used for the detection of a chemical substance, that combines a biological component with a physicochemical detector.
The ''sensitive biological element'', e.g. tissue, microorganisms, organelles, cell rece ...
s to detect contaminants such as herbicides and insecticides. Glutathione transferases are also used in transgenic plants to increase resistance to both biotic and abiotic stress. Glutathione transferases are currently being explored as targets for anti-cancer medications due to their role in drug resistance
Drug resistance is the reduction in effectiveness of a medication such as an antimicrobial or an antineoplastic in treating a disease or condition. The term is used in the context of resistance that pathogens or cancers have "acquired", that is, ...
. Further, glutathione transferase genes have been investigated due to their ability to prevent oxidative damage
Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal r ...
and have shown improved resistance in transgenic
A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the ...
cultigen
A cultigen () or cultivated plant is a plant that has been deliberately altered or selected by humans; it is the result of artificial selection. These plants, for the most part, have commercial value in horticulture, agriculture or forestry. Beca ...
s.
Rubber transferases
Currently the only available commercial source of natural rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
is the ''Hevea
''Hevea'' is a genus of flowering plants in the spurge family, Euphorbiaceae, with about ten members. It is also one of many names used commercially for the wood of the most economically important rubber tree, '' H. brasiliensis''. The genus is n ...
'' plant (''Hevea brasiliensis''). Natural rubber is superior to synthetic rubber
A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubbe ...
in a number of commercial uses. Efforts are being made to produce transgenic plants capable of synthesizing natural rubber, including tobacco
Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...
and sunflower
The common sunflower (''Helianthus annuus'') is a large annual forb of the genus ''Helianthus'' grown as a crop for its edible oily seeds. Apart from cooking oil production, it is also used as livestock forage (as a meal or a silage plant), as ...
. These efforts are focused on sequencing the subunits of the rubber transferase enzyme complex in order to transfect these genes into other plants.
Membrane-associated transferases
Many transferases associate with biological membranes
A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the ce ...
as peripheral membrane protein
Peripheral membrane proteins, or extrinsic membrane proteins, are membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the periph ...
s or anchored to membranes through a single transmembrane helix
A transmembrane domain (TMD) is a membrane-spanning protein domain. TMDs generally adopt an alpha helix topological conformation, although some TMDs such as those in porins can adopt a different conformation. Because the interior of the lipid bi ...
,Superfamilies of single-pass transmembrane transferases
in Membranome database
Membranome database provides structural and functional information about more than 6000 single-pass (bitopic) transmembrane proteins from ''Homo sapiens'', ''Arabidopsis thaliana'', ''Dictyostelium discoideum'', ''Saccharomyces cerevisiae'', '' ...
for example numerous
glycosyltransferases
Glycosyltransferases (GTFs, Gtfs) are enzymes ( EC 2.4) that establish natural glycosidic linkages. They catalyze the transfer of saccharide moieties from an activated nucleotide sugar (also known as the " glycosyl donor") to a nucleophilic gly ...
in
Golgi apparatus
The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ins ...
. Some others are multi-span
transmembrane proteins
A transmembrane protein (TP) is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequentl ...
, for example certain
oligosaccharyltransferase
Oligosaccharyltransferase or OST () is a membrane protein complex that transfers a 14-sugar oligosaccharide from dolichol to nascent protein. It is a type of glycosyltransferase. The sugar Glc3Man9GlcNAc2 (where Glc=Glucose, Man=Mannose, and GlcN ...
s or microsomal
glutathione S-transferase
Glutathione ''S''-transferases (GSTs), previously known as ligandins, are a family of eukaryotic and prokaryotic phase II metabolic isozymes best known for their ability to catalyze the conjugation of the reduced form of glutathione (GSH) to x ...
from
MAPEG family
In molecular biology the MAPEG (Membrane-Associated Proteins in Eicosanoid and Glutathione metabolism) family of proteins are a group of membrane associated proteins with highly divergent functions. Included are the 5-lipoxygenase-activating prot ...
.
References
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