[Free radicals in the flavin reduction reaction. Interaction of reduced nicotinamide adenine dinucleotide with flavin in solution].

The study of the flavin mononucleotide (FMN)-reduced nicotinamide adeninedinucleotide (NADH) reaction was carried out both under aerobic and anaerobic conditions, using spectrophotometric and titrimetric methods. The consumption of NADH was shown to exceed two times the consumption of FMN in the anaerobic reaction and the rate constant in the aerobic reaction was found to be about 4 times of that of the anaerobic reaction. Moreover, the replacement of anaerobic conditions by aerobic ones at pH 5.0 resulted in a considerable increase of proton consumption rate in the reaction course. The data obtained are contradictory to the generally accepted hypothesis of hydrid-ion transfer in the reaction of NADH oxidation. It was assumed that this reaction proceeded through a homolytic pathway.