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|Section2= |Section3= }} Inosinic acid or inosine monophosphate (IMP) is a nucleoside monophosphate. Inosinic acid is important in metabolism. It is the ribonucleotide of hypoxanthine and the first nucleotide formed during the synthesis of purine. It is formed by the deamination of adenosine monophosphate, and is hydrolysed from inosine. IMP is an intermediate ribonucleoside monophosphate in purine metabolism. The enzyme deoxyribonucleoside triphosphate pyrophosphohydrolase, encoded by YJR069C in ''Saccharomyces cerevisiae'' and containing (d)ITPase and (d)XTPase activities, hydrolyses ITP releasing pyrophosphate and IMP. Important derivatives of inosinic acid include 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 flavour enhancers. ==Inosinate synthesis== The inosinate synthesis is complex, beginning with a 5-phosphoribosyl-1-pyrophosphate (PRPP). In the first step, an amino group given by glutamine is attached at carbon 1 of PRPP. The resulting molecule is 5-phosphoribosylamine, which is highly unstable, with a half-life of 30 seconds at physiologic pH. 5-Phosphoribosylamine gains an amino acid (glycine), becoming glycinamide ribonucleotide (GAR). Then, N10-formyltetrahydrofolate (Tetrahydrofolate) transfers a formyl group to glycinamide ribonucleotide to form formyl glycinamide ribonucleotide (FGAR). Using an ATP molecule, glutamine donates an ammonia molecule which is added to the compound forming formylglycinamidine ribonucleotide. Another ATP molecule causes an intermolecular reaction that produces an imidazole ring (5-aminoimidazole ribonucleotide). The next step of the pathway is adding bicarbonate to make carboxyaminoimidazole ribonucleotide by using ATP (it only happens in fungi and bacteria; high eukaryotes simply add CO2 to form the ribonucleotide). Then, the imidazole’s carboxylate group phosphatises and adds aspartate. As we have just seen, a six-step process links glycine, formate, bicarbonate, glutamine, and aspartate to lead to an intermediate that contains almost all the required atoms to synthesize a purine ring. This intermediate removes fumarate, and a second formyl group from THF is added. The compound gets cycled and forms inosinate after a sort of intermolecular reactions. Inosinate is the first intermediate in this synthesis pathway to have a whole purine ring. Enzymes taking part in IMP synthesis constitute a multienzyme complex in the cell. Evidences demonstrate that there are multifunctional enzymes, and some of them catalyze non-sequential steps in the pathway. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「inosinic acid」の詳細全文を読む スポンサード リンク
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