Abstract
Structural and serological characteristics of the three Bacillus subtilis dehydrogenases: alanine dehydrogenase (L-alanine: NAD oxidoreductase (deaminating), EC 1.4.1.1), malate dehydrogenase (L-malate:NAD oxidoreductase, EC 1.1.1.37) and lactate dehydrogenase (L-lactate : NAD oxidoreductase, EC 1.1.1.27) were investigated using pure crystalline enzyme preparations. Serological cross reaction was observed between alanine dehydrogenase and malate dehydrogenase, and between malate dehydrogenase and lactate dehydrogenase (that between alanine dehydrogenase and lactate dehydrogenase being weaker). Alanine dehydrogenase (mol. wt., 228 000) is composed of six identical (or nearly identical) subunits; malate dehydrogenase (mol. wt., 148000) is composed of four identical (or nearly identical) subunits, and lactate dehydrogenase (mol. wt., 146 000) also has four identical (or nearly identical) subunits. The amino acid compositions of these subunits are significantly different, but their subunit molecular weights are approximately the same. On fingerprinting, alanine dehydrogenase and malate dehydrogenase have at least four spots in common, and lactate dehydrogenase has two of these spots. The three enzymes are closely similar with respect to the availability of NAD and NAD analogs as substrates. On the basis of the structural and serological similarity, evolutionary implications of the dehydrogenases are discussed.
Published Version
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