A specific enzyme is not necessary for vanadate-induced oxidation of NADH

It has recently been found that ortho- or metavanadate can effectively block (Na+ + K+)ATPase and that it loses its blocking potency when reduced to the vanadyl (VO2+) ion. The question arose whether vanadate could be involved (reduced) in an NAD-linked enzymatic redox system of the cell. Here we have studied the effect of vanadate on malate dehydrogenase (MDH, EC1.1.1.37) catalysed oxidation of NADH during the formation of malate from oxalacetate in vitro. The MDH reaction was accelerated by vanadate, but we found thatr vanadate does not require the presence of any specific enzyme or substrate to mediate NADH oxidation.