Mechanistic and Stereochemical Studies on the Glycine Reductase of Clostridium sticklandii

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Abstract
Clostridial glycine reductase multienzyme complex which catalyses the reaction; Glycine + ADP + Pi + 2H .fwdarw. Acetate + ATP + NH3, was solubilized and fractionated essentially according to the method of Stadtman into 2 components: protein A and ''glycine reductase'' fraction. A reconstituted system obtained by combining the 2 components in the presence of dithiothreitol catalyzed the conversion of glycine into acetate concomitant with the phosphorylation of ADP to ATP. Using the reconstituted system, in which the unwanted enzymic activity catalyzing an exchange of the .alpha.-H atoms of glycine with the protons of the medium had been greatly reduced, the conversion of (2RS)-[2-14C, 2-3H1]glycine (3H/14C = 7.16) into acetate (3H/14C = 7.03) was attended by the retention of both the C-2 H atoms of glycine. Conversion of (2S)-[2-2H1,2-3H1]glycine and (2R)-[2-2H1, 2-3H1]glycine by the reconstituted system gave (2S)-acetate and (2R)-acetate, respectively, showing that the reductive deamination of glycine occurs through an inversion of configuration. The cumulative information available on the glycine reductase reaction is embodied in a hypothetical mechanism of action for the enzyme.