FORMATION OF NITRIC OXIDE MYOGLOBIN - MECHANISMS OF REACTION WITH VARIOUS REDUCTANTS

SUMMARY– The concentration, temperature and pH dependences of the formation of nitric oxide myoglobin (NOMb) from metmyoglobin nitrite (MetMb·NO2) were determined for nitrite and the reductants, ascorbic acid, cysteine, hydro‐quinone, nicotinamide adenine dinucleotide (NADH) and glyceraldehyde. The reaction for all reductants except glyceraldehyde involves the production of a nitroso‐reductant intermediate which breaks down to release nitric oxide. The latter forms a nitric oxide metheme complex (Fe+++) which is then reduced to the ferrous state (Fe++). With cysteine and NADH there is a second pathway which probably involves the direct reduction of MetMb NO2. Ascorbate and hydro‐quinone form nitroso intermediates that are stabilized in alkali. The effects of oxygen, ethylenediaminetetraacetic acid and cytochrome c on the reaction were determined. Oxygen slows or inhibits the reaction, while the latter two have no effect on the reaction as studied. Copyright © 1968, Wiley Blackwell. All rights reserved