Purification and Chemical Characterization of Malate Dehydrogenase of Bacillus subtilis

In an attempt to elucidate the relationships between some pyridine nucleotide-dependent dehydrogenases in Bacillus subtilis, such as alanine dehydrogenase, malate dehydrogenase, lactate dehydrogenase, and glutamate dehydrogenase, these enzymes are being purified and characterized with respect to their chemical, serological, and enzymic properties. In two previous papers (1, 2), the purification and properties of alanine dehydrogenase have been reported. This paper elaborates the isolation and crystallization of malate dehydrogenase (L-malate:NAD oxidoreductase, EC 1.1.1.37) as well as its molecular weight and amino acid composition. Although malate dehydrogenase activity in microorganisms is usually higher than that of several other dehydrogenases which participate in the tricarboxylic acid cycle, it has not yet, to the author’s knowledge, been purified from bacteria, nor have its chemical and enzymic properties been reported. B. subtilis strain 60-180 (a derivative of the Marburg strain), as well aas other Marburg derivatives, produces malate dehydrogenaee “constitutively”: the malate dehydrogenase activity is much stronger than that of alanine dehydrogenase and lactate dehydrogenase if the latter enzymes are not induced or derepressed. The enzyme can therefore be obtained in large quantities from ba,ct,eria grown in any growth medium.