CHANGES IN OPTICAL ROTATORY DISPERSION INDUCED BY DILUTION INACTIVATION OF DEHYDROGENASES

Optical rotatory dispersion properties of 3 dehydrogenases of Bacillus subtilis were examined under various conditions. Alanine dehydrogenase (L-alanine: NAD+ oxidoreductase, deaminating, EC 1.4.1.1), which consisted of 6 subunits, and lactate dehydrogenase (L-lactate: NAD+oxidoreductase, EC 1.1.1.27), which consisted of 4 subunits, were partially inactivated by dilution at neutral pH. No significant changes in their optical rotatory dispersions and in their molecular weights accompanying the dilution inactivation were detected. Lactate dehydrogenase was completely inactivated by dilution at alkaline pH accompanied by dissociation into subunits. A change in optical rotatory dispersion, which indicated unfolding of the enzyme, was observed. Malate dehydrogenase (L-malate: NAD+ oxidoreductase, EC 1.1.1.37), which consisted of 4 subunits, was completely inactivated by dilution at alkaline pH in the absence of NADH accompanied by dissociation into subunits. A change in optical rotatory dispersion, suggesting unfolding and B-structure formation, was observed.