Glutamic–alanine and glutamic–aspartic transaminases of wheat germ

Abstract

The transamination reactions (1) L-glutamic acid + pyruvic acid [image] [alpha]-oxoglutaric acid + L-alanine (catalyzed by glutamic-alanine transaminase) and (2) L-glutamic acid + oxaloacetic acid [image] [alpha]-oxoglutaric acid + L-aspartic acid (catalyzed by glutamic-aspartic transaminase) were studied with partially purified enzyme preparations from wheat germ. The glutamic-alanine transaminase has an equilibrium constant of 1.4 at 25[degree] and pH 7.5, and an optimum pH of 7.5. The glutamic-aspartic enzyme has an equilibrium constant of 5.0 at 25[degree] and pH 8 and an optimum pH between 8.0 and 8.5. The effect of pyridoxal phosphate and some inhibitors on the transaminases suggests that the 2 systems may be catalyzed by 2 different enzymes, as are the animal glutamic-alanine and glutamic-aspartic transaminase systems.