Determination of aspartic and glutamic acids by enzymatic decarboxylation.

Suspensions of Clostridium welchii (strain SR 12) quantitatively decarboxylate the L isomers of aspartic (1) and glutamic acids (2) to ar-alanine and y-aminobutyric acid, respectively. Although a quantitative procedure for the determination of glutamic acid based upon decarboxylation with this organism has been described (3), it has been found that aspartic acid, especially in the presence of cr-keto acids, is also decarboxylated under the conditions of this procedure (1). In the present communication, methods for the separate determination of aspartic and glutamic acids by decarboxylation with C. welchii are described. Glutamic acid may be determined in the presence of aspartic and keto acids by inhibition of aspartic decarboxylase with semicarbazide or cetyltrimethylammonium bromide. Determinations of aspartic acid in the absence of glutamic acid may conveniently be performed with the same bacterial suspension, provided small amounts of pyruvate are added. Determinations of aspartic and glutamic acids on the same aliquot can be achieved by utilizing the fact that inhibition of aspartic decarboxylase by semicarbazide is reversible by pyruvate.