NADH OXIDATION IS STIMULATED BY AN INTERMEDIATE FORMED DURING VANADYLH2O2 INTERACTION

Addition of NADH decreased the oxygen release that accompanied oxidati on of vanadyl by H2O2. The added NADH was oxidized rapidly and oxygen was consumed with a stoichiometry of 1:1 for NADH/O-2. Small concentra tions of H2O2 were sufficient to trigger this oxygen-consuming NADH ox idation which terminated on exhaustion of either NADH or vanadyl. The oxidation of NADH increased proportionately with concentration of NADH and vanadyl. The oxidation products of vanadyl were found to be a mix ture of vanadate oligomers and peroxovanadates. The reaction was sensi tive to catalase, SOD, histidine and EDTA. Using ESR spectroscopy with DMPO as the spin trap, an adduct corresponding to DMPO-OH was detecte d in these phosphate-buffered reaction mixtures. Participation of hydr oxyl radicals in NADH oxidation, however, seems doubtful because even high concentrations of ethanol, methanol, mannitol, formate and benzoa te, known to scavenge these radicals, did not block the reaction. The results indicate that peroxovanadate intermediates formed during vanad yl oxidation by H2O2 play a key role in the oxidation of NADH.