Nicotinic Acid Metabolism. 2,3-Dimethylmalate Lyase

Abstract

A new enzyme, 2,3-dimethylmalate lyase, was purified from Clostridium barkeri to about 80% homogeneity. Some of the properties of the enzyme are described. The 2,3-dimethylmalic acid (m.p. [melting point] 143.degree. C) described in the literature represents only 1 racemic pair. This pair is not attacked by 2,3-dimethylmalate lyase. The isolation of both racemic pairs of 2,3-dimethylmalic acid is described. Half of 1 pair, m.p. 104-106.degree. C, was converted to propionate and pyruvate by 2,3-dimethylmalate lyase. In combination with earlier works, the results established 2,3-dimethylmalte as an intermediate in the degradation of nicotinic acid by C. barkeri. Experimental evidence indicates that 2,3-dimethylmalate lyase is not an acyl-S-enzyme and it is different in this respect and in quaternary structure from the apparently related enzymes citrate lyase [EC 4.1.3.6] and citramalate lyase [EC 4.1.3.22].