[Oxidation of NADH by singlet oxygen generated by triplet flavin]

Mechanisms of NADH oxidation in the presence of flavines in the light under aerobic and anaerobic conditions has been studied by spectrophotometry method and by registering the kinetics of changes in pH, luminescence and oxygen content in solution. It is shown that singlet oxygen O2* generated by triplet flavine may be an agent that immediately oxidizes NADH under aerobic conditions. The rate constant of the reaction of O2* with NADH accounts for about 1.9 . 10(9) M-1 s-1 and maximum quantum yield of NADH photooxidation in the presence of flavine mononucleotide is 0.7. During aerobic oxidation of NADH the flavine molecules function as photosensitizers rather than as carriers of reduced equivalents.