Mechanistic studies on the reaction of nitroxylcobalamin with dioxygen: evidence for formation of a peroxynitritocob(III)alamin intermediate.
Studies by others suggest that the reduced vitamin B12 complex, cob(II)alamin, scavenges nitric oxide to form air-sensitive nitroxylcobalamin (NO(-)-Cbl(III); NOCbl) in vivo. The fate of newly formed NOCbl is not known. A detailed mechanistic investigation of the oxidation of NOCbl by oxygen is presented. Only base-on NOCbl reacts with O2, and the reaction proceeds via an associative mechanism involving a peroxynitritocob(III)alamin intermediate, Co(III)-N(O)OO(-). The intermediate undergoes O-O bond homolysis and ligand isomerization to ultimately yield NO2Cbl and H2OCbl(+)/HOCbl, respectively. Ligand isomerization may potentially occur independent of O-O bond homolysis. Formation of (•)OH and (•)NO2 intermediates from O-O bond homolysis is demonstrated using phenol and tyrosine radical traps and the characterization of small amounts of a corrinoid product with minor modifications to the corrin ring.
Department of Chemistry and Biochemistry and ‡School of Biomedical Sciences, Kent State University , Kent, Ohio 44242, United States.
Harishchandra
H
Subedi
Nicola E
NE
Brasch
D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000737:chemistry*
D009589:Nitrogen Oxides; C039900:nitroxyl; D014805:Vitamin B 12; D010100:Oxygen