Purification and Properties of Glycine Decarboxylase, a Component of the Glycine Cleavage System, from Rat Liver Mitochondria and Immunochemical Comparison of This Enzyme from Various Sources

Abstract

Glycine decarboxylase, tentatively called P-protein as a constituent of the glycine cleavage system, was purified to near homogeneity from rat liver mitochondria. The purified P-protein was a homodimer with a molecular weight of about 210, 000, consisting of identical subunits with a molecular weight of 105, 000. In the exchange reaction of the carboxyl carbon of glycine with CO₂ catalyzed by the purified P-protein in the presence of H-protein, the pH optimum was 6.7, K_m for glycine was 6.6mM, and Km for H-protein was 7.4 μm. A specific rabbit antibody against the purified rat liver P-protein was prepared. Ouchterlony double diffusion analysis and immunoinhibition experiments using this antibody revealed immuno-logical cross-reactivity among the P-proteins from various species of animals such as carp, frog, snake, chicken, bovine, and human, suggesting a quite conservative evolution of the glycine cleavage system.