title: Nicotinic acid metabolism. 2,3-Dimethylmalate lyase.
abstract: 1) 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. 2) It is shown that the 2,3-dimethylmalic acid (m.p. 143 degrees C) described in the literature represents only one racemic pair. This pair is not attacked by 2,3-dimethylmalate lyase. 3) The isolation of both racemic pairs of 2,3-dimethylmalic acid is described. Half of one pair, m.p. 104-106 degrees C, was converted to propionate and pyruvate by 2,3-dimethylmalate lyase. 4) In combination with earlier work performed by E.R. Stadtman and coworkers the results given under points 1--3 establish 2,3-dimethylmalate as an intermediate in the degradation of nicotinic acid by C. barkeri. 5) Experimental evidence indicates the 2,3-dimethylmalate lyase is no acyl-S-enzyme and that it is different in this respect as well as in quaternary structure from the apparently related enzymes citrate lyase and citramalate lyase.
mesh_terms: D003013:Clostridium / Q000201:enzymology*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008293:Malates; D008970:Molecular Weight; D009539:Nicotinic Acids / Q000378:metabolism*; D007652:Oxo-Acid-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D008293:Malates; D009539:Nicotinic Acids; D007652:Oxo-Acid-Lyases