Reversible conversion of nitroxyl anion to nitric oxide by superoxide dismutase.
Superoxide dismutase (SOD) rapidly scavenges superoxide (O2-) and also prolongs the vasorelaxant effects of nitric oxide (NO), thought to be the endothelium-derived relaxing factor. This prolongation has been ascribed to prevention of the reaction between O2- with NO. We report that SOD supports a reversible reduction of NO to NO-. When cyanamide and catalase were used to generate NO- in the presence of SOD, NO was measured by the conversion of HbO2 to MetHb. When SOD[Cu(I)] was exposed to NO anaerobically, NO- was trapped by MetHb forming nitrosylmyoglobin. When NO was generated by 3-morpholinosydnonimine hydrochloride in the presence of SOD, NO- or a similar reductant was formed, which reduced catalase compound II and promoted the formation of the catalase [Fe(III)]-NO complex. It is, therefore, conceivable that SOD may protect NO and endothelium-derived relaxing factor by a mechanism in addition to O2- scavenging and that NO- may be a physiologically important form of endothelium-derived relaxing factor.
Murphy
M E
ME
Institut für Physiologische Chemie I, Universität Düsseldorf, Federal Republic of Germany.
Sies
H
H
D000818:Animals; D002374:Catalase / Q000378:metabolism*; D002417:Cattle; D003300:Copper / Q000494:pharmacology; D004912:Erythrocytes / Q000201:enzymology; D005609:Free Radicals; D007527:Isoenzymes / Q000097:blood / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism*; D009589:Nitrogen Oxides / Q000378:metabolism*; D010108:Oxyhemoglobins / Q000378:metabolism; D013053:Spectrophotometry; D013482:Superoxide Dismutase / Q000097:blood / Q000378:metabolism*
D005609:Free Radicals; D007527:Isoenzymes; D009589:Nitrogen Oxides; D010108:Oxyhemoglobins; D009569:Nitric Oxide; D003300:Copper; D002374:Catalase; D013482:Superoxide Dismutase; C039900:nitroxyl