Inosinate, histidine

The 5 -Nucleotides. Also dating back many years in the Far East was the knowledge that bonita tuna possesses a substance that very effectively enhances the flavor of foods. However, it was not until 1913 dial S. Kodama (Tokyo University) commenced a serious investigation directed toward identifying and isolating the substance from tuna. Initially. Kodama believed that the substance was the histidine salt of 5 -inosinic acid, but later found that the substance was actually 5 -inosinic acid itself. This nucleotide was found to be many more times as effective as MSG. Further research by Kodama and others has shown that these nucleotides are present in many natural foods. 

J. W. Larson, Y. B. Tewari, and R. N. Goldberg, Thermodynamics of the reactions between adenosine, adenosine 5 -monophosphate, in-osine, and inosine 5 -monophosphate. The conversion of L-histidine to (urocanic acid and ammonia) J. Chem. Thermodvn. 25. 73 90 (1993). 

In some microorganisms the conversion of adenylate to inosinate takes place via the reactions of histidine synthesis from ATP, as described in Chapter 3. 

Phosphorylation at the carboxylate (ATP ADP) followed by reaction with aspartate (Asp,D) in the presence of phosphoribosylaminoimidazolesuccinocarbox-amide synthase (EC 6.S.2.6) produces the corresponding (S)-succinate derivative. This is followed by loss of fumarate (adenylosuccinate lyase, EC 4.S.2.2) to the corresponding amide (last seen in the biosynthesis of histidine (His, H) (Scheme 12.26). Then, as shown in Scheme 12.97, N-formylation (as in Scheme 12.87) on the C-5 amino group is effected with IO-CHO-H4 folate (EC 2.1.2.3) to yield the N-formyl derivative (5-formamido-l-(5 -phosphoribosyl) imidazole-4-carboxyamide). Loss of water accompanies cyclization (EC 3.5.2.10) to yield inosine 5 -phosphate (IMP). 

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