Glutamic–oxaloacetic transaminase of cauliflower. 1. Purification and specificity

Abstract

Glutamic-oxaloacetic transaminase has been purified 250-fold from cauliflower florets; the purified enzyme is free from glutamic-pyruvic transaminase. Purified preparations of the enzyme catalyse transaminations between gamma-hydroxyglutamate, gamma-methy-leneglutamate, [beta]-hydroxyasparate, cysteate and cysteinesulphinate as amino-group donors, and both [alpha]-oxoglutarate and oxaloacetate as amino-group acceptors; oxomalonate is a good inhibitor but a poor substrate. Kinetic data, and the constancy of ratios throughout purification, strongly suggest that one enzyme is involved in transaminations between glutamate, cysteate, cysteinesulphinate and oxaloacetate. The substrate specificity of purified pig-heart transaminase is similar to that of the enzyme from cauliflower, except that oxomaionate is a better substrate for the pig-heart enzyme. The possibility that the transamination of cysteinsulphinic acid may be involved in the pathway of sulphur reduction is discussed.