Glycine metabolism by rat liver mitochondria: Isolation and some properties of the protein-bound intermediate of the reversible glycine cleavage reaction

Abstract

Appropriate combinations of purified components of the reversible glycine cleavage system of rat liver catalyze three partial reactions: (1) decarboxylation of glycine or its reverse reaction catalyzed by P- and H-protein, (2) condensation of one carbon substrate and ammonia or its reverse reaction catalyzed by T- and H-protein, and (3) oxidation and reduction of active disulfide of H-protein catalyzed by L-protein. Reactions (1) and (2) give the same product which is bound to H-protein. The protein-bound product was isolated by gel filtration and converted to glycine by incubation with P-protein and CO 2 or degraded further to one carbon unit and ammonia by incubation with T-protein and tetrahydrofolate. The data are consistent with the conclusion that the enzyme-bound product is an intermediate in the reversible glycine cleavage reaction. A scheme is presented for the reactions catalyzed by the enzyme system.