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Morpheein
Morpheeins are proteins that can form two or more different homo-oligomers (morpheein forms), but must come apart and change shape to convert between forms. The alternate shape may reassemble to a different oligomer. The shape of the subunit dictates which oligomer is formed. Each oligomer has a finite number of subunits (stoichiometry). Morpheeins can interconvert between forms under physiological conditions and can exist as an equilibrium of different oligomers. These oligomers are physiologically relevant and are not misfolded protein; this distinguishes morpheeins from prions and amyloid. The different oligomers have distinct functionality. Interconversion of morpheein forms can be a structural basis for allosteric regulation, an idea noted many years ago, and later revived. A mutation that shifts the normal equilibrium of morpheein forms can serve as the basis for a conformational disease. Features of morpheeins can be exploited for drug discovery. The dice image (F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morpheein Dice
Morpheeins are proteins that can form two or more different homo-oligomers (morpheein forms), but must come apart and change shape to convert between forms. The alternate shape may reassemble to a different oligomer. The shape of the subunit dictates which oligomer is formed. Each oligomer has a finite number of subunits (stoichiometry). Morpheeins can interconvert between forms under physiological conditions and can exist as an equilibrium of different oligomers. These oligomers are physiologically relevant and are not misfolded protein; this distinguishes morpheeins from prions and amyloid. The different oligomers have distinct functionality. Interconversion of morpheein forms can be a structural basis for allosteric regulation, an idea noted many years ago, and later revived. A mutation that shifts the normal equilibrium of morpheein forms can serve as the basis for a conformational disease. Features of morpheeins can be exploited for drug discovery. The dice image (F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allosteric Regulation
In biochemistry, allosteric regulation (or allosteric control) is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site. The site to which the effector binds is termed the ''allosteric site'' or ''regulatory site''. Allosteric sites allow effectors to bind to the protein, often resulting in a conformational change and/or a change in protein dynamics. Effectors that enhance the protein's activity are referred to as ''allosteric activators'', whereas those that decrease the protein's activity are called ''allosteric inhibitors''. Allosteric regulations are a natural example of control loops, such as feedback from downstream products or feedforward from upstream substrates. Long-range allostery is especially important in cell signaling. Allosteric regulation is also particularly important in the cell's ability to adjust enzyme activity. The term ''allostery'' comes from the Ancient Greek ''allos'' (), "other", and ''stereos' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porphobilinogen Synthase
Aminolevulinic acid dehydratase (porphobilinogen synthase, or ALA dehydratase, or aminolevulinate dehydratase) is an enzyme () that in humans is encoded by the ''ALAD'' gene. Porphobilinogen synthase (or ALA dehydratase, or aminolevulinate dehydratase) synthesizes porphobilinogen through the asymmetric condensation of two molecules of aminolevulinic acid. All natural tetrapyrroles, including hemes, chlorophylls and vitamin B12, share porphobilinogen as a common precursor. Porphobilinogen synthase is the prototype morpheein. Function It catalyzes the following reaction, the second step of the biosynthesis of porphyrin: :2 5-Aminolevulinic acid \rightleftharpoons porphobilinogen + 2 H2O It therefore catalyzes the condensation of 2 molecules of 5-aminolevulinate to form porphobilinogen (a precursor of heme, cytochromes and other hemoproteins). This reaction is the first common step in the biosynthesis of all biological tetrapyrroles. Zinc is essential for enzymatic activity. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cystathionine Beta-synthase
Cystathionine-β-synthase, also known as CBS, is an enzyme () that in humans is encoded by the ''CBS'' gene. It catalyzes the first step of the transsulfuration pathway, from homocysteine to cystathionine: : L-serine + L-homocysteine \rightleftharpoons L-cystathionine + H2O CBS uses the cofactor pyridoxal-phosphate (PLP) and can be allosterically regulated by effectors such as the ubiquitous cofactor S-adenosyl-L-methionine (adoMet). This enzyme belongs to the family of lyases, to be specific, the hydro-lyases, which cleave carbon-oxygen bonds. CBS is a multidomain enzyme composed of an N-terminal enzymatic domain and two CBS domains. The ''CBS'' gene is the most common locus for mutations associated with homocystinuria. Nomenclature The systematic name of this enzyme class is L-serine hydro-lyase (adding homocysteine; L-cystathionine-forming). Other names in common use include: * β-thionase, * cysteine synthase, * L-serine hydro-lyase (adding homocysteine), * methylcys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
3-oxoacid CoA-transferase
In enzymology, a 3-oxoacid CoA-transferase () is an enzyme that catalyzes the chemical reaction :succinyl-CoA + a 3-oxo acid \rightleftharpoons succinate + a 3-oxoacyl-CoA Thus, the two substrates of this enzyme are succinyl-CoA and 3-oxo acid, whereas its two products are succinate and 3-oxoacyl-CoA. This enzyme belongs to the family of transferases, specifically the CoA-transferases. The systematic name of this enzyme class is succinyl-CoA:3-oxo-acid CoA-transferase. Other names in common use include 3-oxoacid coenzyme A-transferase, 3-ketoacid CoA-transferase, 3-ketoacid coenzyme A transferase, 3-oxo-CoA transferase, 3-oxoacid CoA dehydrogenase, acetoacetate succinyl-CoA transferase, acetoacetyl coenzyme A-succinic thiophorase, succinyl coenzyme A-acetoacetyl coenzyme A-transferase, and succinyl-CoA transferase. This enzyme participates in 3 metabolic pathways: synthesis and degradation of ketone bodies, valine, leucine and isoleucine degradation, and butanoate metabolis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanovirin-N
Cyanovirin-N (CV-N) is a protein produced by the cyanobacterium '' Nostoc ellipsosporum'' that displays virucidal activity against several viruses, including human immunodeficiency virus (HIV). The virucidal activity of CV-N is mediated through specific high-affinity interactions with the viral surface envelope glycoproteins gp120 and gp41, as well as to high-mannose oligosaccharides found on the HIV envelope. In addition, CV-N is active against rhinoviruses, human parainfluenza virus, respiratory syncytial virus, and enteric viruses. The virucidal activity of CV-N against influenza virus is directed towards viral haemagglutinin. CV-N has a complex fold composed of a duplication of a tandem repeat of two homologous motifs comprising three-stranded beta-sheet The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hyd ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Citrate Synthase
The enzyme citrate synthase E.C. 2.3.3.1 (previously 4.1.3.7)] exists in nearly all living cells and stands as a pace-making enzyme in the first step of the citric acid cycle (or Krebs cycle). Citrate synthase is localized within eukaryotic cells in the mitochondrial matrix, but is encoded by nuclear DNA rather than mitochondrial. It is synthesized using cytoplasmic ribosomes, then transported into the mitochondrial matrix. Citrate synthase is commonly used as a quantitative enzyme marker for the presence of intact mitochondria. Maximal activity of citrate synthase indicates the mitochondrial content of skeletal muscle. The maximal activity can be increased by endurance training or high-intensity interval training, but maximal activity is further increased with high-intensity interval training. Citrate synthase catalyzes the condensation reaction of the two-carbon acetate residue from acetyl coenzyme A and a molecule of four-carbon oxaloacetate to form the six-carbon citrate: ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chorismate Mutase
In enzymology, chorismate mutase () is an enzyme that catalyzes the chemical reaction for the conversion of chorismate to prephenate in the pathway to the production of phenylalanine and tyrosine, also known as the shikimate pathway. Hence, this enzyme has one substrate, chorismate, and one product, prephenate. Chorismate mutase is found at a branch point in the pathway. The enzyme channels the substrate, chorismate to the biosynthesis of tyrosine and phenylalanine and away from tryptophan. Its role in maintaining the balance of these aromatic amino acids in the cell is vital. This is the single known example of a naturally occurring enzyme catalyzing a pericyclic reaction. Chorismate mutase is only found in fungi, bacteria, and higher plants. Some varieties of this protein may use the morpheein model of allosteric regulation. Protein family This enzyme belongs to the family of isomerases, specifically those intramolecular transferases that transfer functional groups. The sys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biotin—(acetyl-CoA-carboxylase) Ligase
In enzymology, a biotin— cetyl-CoA-carboxylaseligase () is an enzyme that catalyzes the chemical reaction :ATP + biotin + apo- cetyl-CoA:carbon-dioxide ligase (ADP-forming)\rightleftharpoons AMP + diphosphate + cetyl-CoA:carbon-dioxide ligase (ADP-forming) The 3 substrates of this enzyme are ATP, biotin, and apo- cetyl-CoA:carbon-dioxide ligase (ADP-forming) whereas its 3 products are AMP, diphosphate, and acetyl-CoA:carbon-dioxide ligase (ADP-forming). This enzyme belongs to the family of ligases, specifically those forming generic carbon-nitrogen bonds. This enzyme participates in biotin metabolism. This protein may use the morpheein model of allosteric regulation. Nomenclature The 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 ... of this enzyme class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ATPase
ATPases (, Adenosine 5'-TriPhosphatase, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, SV40 T-antigen, ATP hydrolase, complex V (mitochondrial electron transport), (Ca2+ + Mg2+)-ATPase, HCO3−-ATPase, adenosine triphosphatase) are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion or the inverse reaction. This dephosphorylation reaction releases energy, which the enzyme (in most cases) harnesses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life. Some such enzymes are integral membrane proteins (anchored within biological membranes), and move solutes across the membrane, typically against their concentration gradient. These are called transmembrane ATPases. Functions Transmembrane ATPases import metabolites necessary for cell metabolism and export toxins, wastes, and solutes that can hinder cellular processes. An important example is the sodium-potass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aspartokinase
Aspartate kinase or aspartokinase (AK) is an enzyme that catalyzes the phosphorylation of the amino acid aspartate. This reaction is the first step in the biosynthesis of three other amino acids: methionine, lysine, and threonine, known as the "aspartate family". Aspartokinases are present only in microorganisms and plants, but not in animals, which must obtain aspartate-family amino acids from their diet. Consequently, methionine, lysine and threonine are essential amino acids in animals. Nomenclature The generic abbreviation for aspartokinases is AK. However, the nomenclature for aspartokinase genes and proteins varies considerable among species. The main aspatokinases are ''lysC'' (''Bacillus subtilis'', ''Escherichia coli'' and many other bacteria), ''ask'' (''Mycobacterium bovis'', ''Thermus thermophilus''), ''AK1''–''AK3'' (''Arabidopsis thaliana''), ''FUB3'' (''Fusarium'' and ''Gibberella'') and ''HOM3'' (''Saccharomyces cerevisiae''). Additionally, ''apk'' is a synonym ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asparaginase
Asparaginase is an enzyme that is used as a medication and in food manufacturing. As a medication, L-asparaginase is used to treat acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LBL). It is given by injection into a vein, muscle, or under the skin. A pegylated version is also available. In food manufacturing it is used to decrease acrylamide. Common side effects when used by injection include allergic reactions, pancreatitis, blood clotting problems, high blood sugar, kidney problems, and liver dysfunction. Use in pregnancy may harm the baby. As a food it is generally recognized as safe. Asparaginase works by breaking down the amino acid known as asparagine without which the cancer cells cannot make protein. The most common nonhematological adverse reactions of asparaginase erwinia chrysanthemi (recombinant) include abnormal liver test, nausea, musculoskeletal pain, infection, fatigue, headache, febrile neutropenia, pyrexia, hemorrhage (bleeding), stomatitis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
