Purification and Properties of Beef Liver D-Glycerate Dehydrogenase*

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Abstract
An improved procedure for purification of D-glycerate dehydrogenase [EC 1. 1. 1. 29] from beef liver is described. The purified enzyme was proved to be homogeneous by ultracentrifugation and zone electrophoresis. Its molecular weight was determined to be 72,000. The Michaelis constants of the enzyme for DL-glycerate and hydroxcypyruvate were 1.4 mM and 4μM, respectively. The enzyme activity was inhibited by hydroxypyruvate, a substrate, with an inhibition constant of 0.08 mM. Among the many metabolites tested, glycolytic intermediates such as pyruvate, α-D-fructose 1,6-diphosphate, 3-phospho-D-glycerate, 2,3-diphospho-D-glycerate, and 2-phospho-D-glycerate as well as ATP strongly inhibited the enzyme activity in the concentration range from 0.1 to 1 mM. The inhibitory action of pyruvate was affected by the concentrations of the substrate and sodium chloride. Both NAD+ (NADH) and NADP+ [NADPH] could act as coenzymes for the enzyme through NADP+ [NADPH] was less effective than NAD+ [NADH]. In the presence of 1 mM pyruvate, however, NADP+ showed a higher coenzyme activity than NAD+ (NADH). Based on these findings, the possibility is discussed that the nonphosphorylated pathway for L-serine synthesis (including D-glycerate dehydrogenase) is actually responsible for catabolic coversion of L-serine to glycolytic intermediates and the latter act as feedback effectors for this catabolic pathway.

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