Inosinic acid

Inosinic acid
Names
	IUPAC name 5'-Inosinic acid
	Other names IMP,; Hypoxanthine ribotide
Identifiers
CAS Number	131-99-7 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:17202 ;
ChEMBL	ChEMBL1233478 ;
ChemSpider	8264 ;
ECHA InfoCard	100.004.588
E number	E630 (flavour enhancer)
IUPHAR/BPS	5124;
MeSH	Inosine+monophosphate
PubChem CID	8582;
UNII	TAO7US05G5 ;
CompTox Dashboard (EPA)	DTXSID4044294 ;
	InChI InChI=1S/C10H13N4O8P/c15-6-4(1-21-23(18,19)20)22-10(7(6)16)14-3-13-5-8(14)11-2-12-9(5)17/h2-4,6-7,10,15-16H,1H2,(H,11,12,17)(H2,18,19,20)/t4-,6-,7-,10-/m1/s1 Key: GRSZFWQUAKGDAV-KQYNXXCUSA-N ; InChI=1/C10H13N4O8P/c15-6-4(1-21-23(18,19)20)22-10(7(6)16)14-3-13-5-8(14)11-2-12-9(5)17/h2-4,6-7,10,15-16H,1H2,(H,11,12,17)(H2,18,19,20)/t4-,6-,7-,10-/m1/s1 Key: GRSZFWQUAKGDAV-KQYNXXCUBU;
	SMILES O=C3/N=C\Nc1c3ncn1[C@@H]2O[C@@H]([C@@H](O)[C@H]2O)COP(=O)(O)O;
Properties
Chemical formula	C10H13N4O8P
Molar mass	348.208 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Inosinic acid or inosine monophosphate (IMP) is a nucleotide (that is, a nucleoside monophosphate). Widely used as a flavor enhancer, it is typically obtained from chicken byproducts or other meat industry waste. Inosinic acid is important in metabolism. It is the ribonucleotide of hypoxanthine and the first nucleotide formed during the synthesis of purine nucleotides. It can also be formed by the deamination of adenosine monophosphate by AMP deaminase. It can be hydrolysed to inosine.

The enzyme deoxyribonucleoside triphosphate pyrophosphohydrolase, encoded by YJR069C in Saccharomyces cerevisiae and containing (d)ITPase and (d)XTPase activities, hydrolyzes inosine triphosphate (ITP) releasing pyrophosphate and IMP.[1]

Important derivatives of inosinic acid include the purine nucleotides found in nucleic acids and adenosine triphosphate, which is used to store chemical energy in muscle and other tissues.

In the food industry, inosinic acid and its salts such as disodium inosinate are used as flavor enhancers. 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.

This figure shows the pathway described: IMP synthesis.

Adenylate (AMP) and guanylate (GMP) come from inosinate

Within a few steps inosinate becomes AMP or GMP. Both compounds are RNA nucleotides. 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.[2] GMP is formed by the inosinate oxidation to xanthylate (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.

Glutamine-PRPP-amidotransferase

Inosinate takes part in the regulation of purine nucleotide biosynthesis

Inosinate and many other molecules inhibit the synthesis of 5-phosphorybosilamine 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 including disodium inosinate (E631), dipotassium inosinate (E632), and calcium inosinate (E633). These three compounds are used as flavor enhancers for the basic taste umami with a comparatively high effectiveness. They are mostly used in soups, sauces, and seasonings for the intensification and balance of the flavor of meat.

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References

Davies O, Mendes P, Smallbone K, Malys N (2012). "Characterisation of multiple substrate-specific (d)ITP/(d)XTPase and modelling of deaminated purine nucleotide metabolism". BMB Reports. 45 (4): 259–64. doi:10.5483/BMBRep.2012.45.4.259. PMID 22531138.
Voet, D, Voet, J. G., Biochemistry (3rd Edition), John Wiley & Sons, Inc., 2004, pg 1095