Vanadium-Dependent NADH Oxidation Activity

Vanadate-stimulated NAD(P)H oxidation activity was first reported in the erythrocyte membrane [20] and has been found in widely diverse membranes including mammalian rat liver [21], the sugar beet plant [22], and the fungus Saccharomyces cerevisiae [23] membrane. The kinetics of NADH oxidation [24] observed in the presence of vanadate and plasma membranes show a variable lag, with H202 and 

02 being products of the reaction. The reaction is stimulated by a phosphovanadium anhydride when vanadate [V(V)] is added to yeast plasma membranes in phosphate buffer [23], 

Other forms of vanadium have been implicated in the stimulation of the plasma membrane vanadate-dependent NAD(P)H oxidation reaction. Decavanadate has been shown to be a more potent stimulator of the vanadate-dependent NADH oxidation activity than added orthovanadate [30,31], Interestingly, decavanadate reductase activity has been found to be an alternative activity of an NADP-specific isocitrate dehydrogenase [32], Diperoxovanadium derivatives have also been shown to be involved in this type of reaction [33,34], Decavanadate may play a role in the biological role of vanadium, as it is found in yeast cells growing in the presence of orthovanadate [8] and is a potent inhibitor of phosphofructokinase-1, the control step of glycolysis, and other metabolic reactions [35], 

The role of these interesting plasma membrane-dependent, vanadate-stimulated NAD(P)H oxidation reactions in cellular metabolism remains to be elucidated, although multiple interactions with cellular metabolism and components are possible including interactions with xanthine oxidase and lipid peroxidation [24], Decavanadate has been shown to enhance cytochrome c reduction [31], and cytochrome c release from mitochondria is associated with initiation of apoptosis. Perhaps the reduced cytochrome c is more readily released from the mitochondria. With increasing emphasis on the redox properties of vanadium being important in its pharmacological effects, it is quite possible that these reactions, either protein dependent or not, may play a role in therapeutic actions of vanadium. 

2 Vanadium Compounds and Cellular Oxidation-Reduction Metabolism 

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