FORMATION OF NITRIC OXIDE MYOGLOBIN BY NICOTINAMIDE ADENINE DINUCLEOTIDES AND FLAVINS

Abstract

SUMMARY –Formation of nitric oxide myoglobin was studied under anaerobic conditions. NADH (reduced nicotinamide adenine dinucleotide) and NADPH (reduced nicotinamide adenine dinucleotide phosphate) as reducing agents alone did not produce nitric oxide myoglobin from metmyoglobin and nitrite. However, in the presence of FMN (flavin mononucleotide), either NADH or NADPH readily produced nitric oxide myoglobin. FAD (flavin adenine dinucleotide) and riboflavin also were effective for the formation of nitric oxide myoglobin by NADH. In the absence of myoglobin, the NADH‐FMN system did not reduce nitrite to nitric oxide. Similarly, a diaphorasemethylene blue system readily produced nitric oxide myoglobin, but in the absence of myoglobin it did not reduce nitrite to nitric oxide. On the other hand, nitric oxide myoglobin was produced from deoxymyoglobin by the action of nitrite in the absence of reducing agents under anaerobic conditions. Deoxymyoglobin can directly reduce nitrite to nitric oxide; the NADH‐FMN and diaphorase‐methylene blue systems may participate in the formation of nitric oxide myoglobin by means of reduction of metmyoglobin to the deoxy form.