Inosinic acid or inosine monophosphate (IMP) is a
nucleotide
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 biomolecule ...
(that is, a
nucleoside
Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleoti ...
monophosphate). Widely used as a flavor enhancer, it is typically obtained from chicken byproducts or other
meat industry
The meat industry are the people and companies engaged in modern industrialized livestock agriculture for the production, packing, preservation and marketing of meat (in contrast to dairy products, wool, etc.). In economics, the meat industry is ...
waste. Inosinic acid is important in
metabolism
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...
. It is the
ribonucleotide
In biochemistry, a ribonucleotide is a nucleotide containing ribose as its pentose component. It is considered a molecular precursor of nucleic acids. Nucleotides are the basic building blocks of DNA and RNA. Ribonucleotides themselves are basic ...
of
hypoxanthine
Hypoxanthine is a naturally occurring purine derivative. It is occasionally found as a constituent of nucleic acids, where it is present in the anticodon of tRNA in the form of its nucleoside inosine. It has a tautomer known as 6-hydroxypurine. ...
and the first nucleotide formed during the synthesis of
purine
Purine is a heterocyclic aromatic organic compound that consists of two rings ( pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines ...
nucleotides. It can also be formed by the
deamination
Deamination is the removal of an amino group from a molecule. Enzymes that catalyse this reaction are called deaminases.
In the human body, deamination takes place primarily in the liver, however it can also occur in the kidney. In situations of ...
of
adenosine monophosphate
Adenosine monophosphate (AMP), also known as 5'-adenylic acid, is a nucleotide. AMP consists of a phosphate group, the sugar ribose, and the nucleobase adenine; it is an ester of phosphoric acid and the nucleoside adenosine. As a substit ...
by
AMP deaminase
AMP deaminase 1 is an enzyme that in humans is encoded by the ''AMPD1'' gene.
Adenosine monophosphate deaminase is an enzyme that converts adenosine monophosphate (AMP) to inosine monophosphate (IMP), freeing an ammonia molecule in the process.
...
. It can be
hydrolysed
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
to
inosine
Inosine is a nucleoside that is formed when hypoxanthine is attached to a ribose ring (also known as a ribofuranose) via a β-N9- glycosidic bond. It was discovered in 1965 in analysis of RNA transferase.
Inosine is commonly found in tRNAs and is ...
.
The enzyme deoxyribonucleoside triphosphate pyrophosphohydrolase, encoded by YJR069C in ''
Saccharomyces cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have b ...
'' and containing (d)ITPase and (d)XTPase activities, hydrolyzes
inosine triphosphate (ITP) releasing
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 othe ...
and IMP.
Important derivatives of inosinic acid include the purine nucleotides found in
nucleic acids and
adenosine triphosphate
Adenosine triphosphate (ATP) is an organic compound that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis. Found in all known forms o ...
, which is used to store
chemical energy in
muscle and other tissues.
In the food industry, inosinic acid and its
salts
In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively c ...
such as
disodium inosinate
Disodium inosinate (E631) is the disodium salt of inosinic acid with the chemical formula C10H11N4Na2O8P. It is used as a food additive and often found in instant noodles, potato chips, and a variety of other snacks. Although it can be obtained ...
are used as
flavor enhancer
A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of the gust ...
s. It is known as
E number reference E630.
Inosinate synthesis
The inosinate synthesis is complex, beginning with a
5-phosphoribosyl-1-pyrophosphate (PRPP).
Enzymes taking part in IMP synthesis constitute a multienzyme complex in the cell. Evidence demonstrates that there are multifunctional enzymes, and some of them catalyze non-sequential steps in the pathway.
Synthesis of other purine nucleotides
Within a few steps inosinate becomes
AMP #REDIRECT Amp
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or
GMP
GMP may refer to:
Finance and economics
* Gross metropolitan product
* Guaranteed maximum price
* Guaranteed Minimum Pension
Science and technology
* GNU Multiple Precision Arithmetic Library, a software library
* Granulocyte-macrophage progenito ...
.
Both compounds are
RNA 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 with ...
.
AMP differs from inosinate by the replacement of IMP's carbon-6 carbonyl with an amino group. The interconversion of AMP and IMP occurs as part of the
purine nucleotide cycle
Purine is a heterocyclic aromatic organic compound that consists of two rings (pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines a ...
.
[Voet, D, Voet, J. G., Biochemistry (3rd Edition), John Wiley & Sons, Inc., 2004, pg 1095] GMP is formed by the inosinate oxidation to
xanthylate
Xanthosine monophosphate also called Xanthylate is an intermediate in purine metabolism. It is a ribonucleoside monophosphate. It is formed from IMP via the action of IMP dehydrogenase, and it forms GMP
GMP may refer to:
Finance and economics
* ...
(XMP), and afterwards adds an amino group on carbon 2. Hydrogen acceptor on inosinate oxidation is
NAD+. Finally, carbon 2 gains the amino group by spending an ATP molecule (which becomes AMP+2Pi). While AMP synthesis requires GTP, GMP synthesis uses ATP. That difference offers an important regulation possibility.
Regulation of purine nucleotide biosynthesis
Inosinate and many other molecules inhibit the synthesis of 5-
phosphoribosylamine from 5-phosphoribosyl-1-pyrophosphate (PRPP), disabling the enzyme that catalyzes the reaction: glutamine-5-phosphoribosyl-1-pyrophosphate-amidotransferase. In other words, when levels of inosinate are high, glutamine-5-phosphoribosyl-1-pyrophosphate-amidotransferase is inhibited, and, as a consequence, inosinate levels decrease. Also, as a result, adenylate and guanylate are not produced, which means that RNA synthesis cannot be completed because of the lack of these two important RNA nucleotides.
Applications
Inosinic acid can be converted into various
salts
In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively c ...
including
disodium inosinate
Disodium inosinate (E631) is the disodium salt of inosinic acid with the chemical formula C10H11N4Na2O8P. It is used as a food additive and often found in instant noodles, potato chips, and a variety of other snacks. Although it can be obtained ...
(E631),
dipotassium inosinate (E632), and
calcium inosinate (E633). These three compounds are used as
flavor enhancer
A flavoring (or flavouring), also known as flavor (or flavour) or flavorant, is a food additive used to improve the taste or smell of food. It changes the perceptual impression of food as determined primarily by the chemoreceptors of the gust ...
s for the basic taste
umami
Umami ( from ja, 旨味 ), or savoriness, is one of the five basic tastes. It has been described as savory and is characteristic of broths and cooked meats.
People taste umami through taste receptors that typically respond to glutamates and ...
with a comparatively high effectiveness. They are mostly used in soups, sauces, and seasonings for the intensification and balance of the flavor of meat.
See also
References
Further reading
* Berg, Jeremy M.; ''Bioquímica''; Editorial Reverté; 6ena edició; Barcelona 2007.
* Nelson, David L.; ''Principles of biochemistry''; Editorial W.H Freeman and Company; 4th edition; New York 2005.
{{DEFAULTSORT:Inosinic Acid
Food additives
Organic acids
Flavor enhancers
Nucleotides
Purines
E-number additives