Glutamate formation, pyrrolidone carboxylate

IV. Nonenzymic Formation of Pyrrolidone Carboxylic Acid from Glutamic Acid, Glutamine, and Other Compounds... 

Abderhalden and Kautzch (77) reported that the heating of dry glutamic acid to 180°-200° led to the formation of essentially optically inactive pyrrolidone carboxylic acid. They obtained optically active l-pyrrolidone carboxylic acid by heating L-glutamic acid at 150°-160° followed by fractional crystallization of the product. These workers also observed that treatment of optically active pyrrolidone carboxylic acid with strong mineral acid led to its conversion to optically active glutamic... 

Using the data of Wilson and Cannan (18), Cleaves (81) was able to show that the rate of formation of pyrrolidone carboxylic acid from glutamic acid in aqueous solution depends directly on the concentration of the ionic species of glutamic acid in solution. Thus, the reactive species are (I), (II), and (IV), while (III) is relatively unreactive. Protonation of the amino group and dissociation of the y-carboxyl group thus makes these groups less reactive carboxylate ion resonance apparently hinders nucleophilic attack by the amino nitrogen. 

The formation of pyrrolidone carboxylic acid under these conditions has been interpreted to indicate the enzymic formation of an activated glutamate intermediate. The available evidence supports the view that glutamate and ATP interact on the active site of the enzyme to yield en-... 

The hydrolysate is subsequently neutralized to pH 5.8 with sodium or calcium carbonate or with sodium hydroxide solution. In this process, the pH range of 2.5-4 must be passed through as quickly as possible to repress the formation of pyrrolidone carboxylic acid from glutamic acid. The hydroysate is filtered and the filtrate (seasoning) stored. The filtration residue is washed with water and refiltered, if necessary. The diluted filtrate is evaporated and added to the seasoning obtained in the first step. 

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