The non-enzymic oxidation of NADH by nitrosobenzene

Nitrosobenzene caused a biphasic oxidation of NADH or NADPH. The initial rapid phase of this oxidation, which is a stoichiometric reaction, was not associated with oxygen consumption and was unaffected by EDTA. In contrast, the slower phase of the NADH oxidation was inhibited by EDTA. It was associated with oxygen uptake and was catalytic, in the sense that many moles of NADH could be oxidized per mole of nitrosobenzene. Copper catalyzed this reaction. A mechanism which explains these observations is proposed.