Gorbunov NV, Osipov AN, Day BW, Zayas-Rivera B, Kagan VE, Elsayed NM. Reduction of ferrylmyoglobin and ferrylhemoglobin by nitric oxide: a protective mechanism against ferryl hemoprotein-induced oxidations.
Biochemistry 1995;
34:6689-99. [PMID:
7756300 DOI:
10.1021/bi00020a014]
[Citation(s) in RCA: 108] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The reactions of metmyoglobin (metMb) and methemoglobin (metHb), oxidized to their respective oxoferryl free radical species (.Mb-FeIV = O/.Hb-4FeIV = O) by tert-butyl hydroperoxide (t-BuOOH), with nitric oxide (NO.) were studied by a combination of optical, electron spin resonance (ESR), ionspray mass (MS), fluorescence, and chemiluminescence spectrometries to gain insight into the mechanism by which NO. protects against oxidative injury produced by .Mb-FeIV = O/.Hb-4FeIV = O. Oxidation of metMb/metHb by t-BuOOH in a nitrogen atmosphere proceeded via the formation of two protein electrophilic centers, which were heme oxoferryl and the apoprotein radical centered at tyrosine (for the .Mb-FeIV = O form, the g value was calculated to be 2.0057), and was accompanied by the formation of t-BuOOH-derived tert-butyl(per)oxyl radicals. We hypothesized that NO. may reduce both oxoferryl and apoprotein free radical electrophilic centers of .Mb-FeIV = O/.Hb-4FeIV = O and eliminate tert-butyl(per)oxyl radicals, thus protecting against oxidative damage. We found that NO. reduced .Mb-FeIV = O/.Hb-4FeIV = O to their respective ferric (met) forms and prevented the following: (i) oxidation of cis-parinaric acid (PnA) in liposomes, (ii) oxidation of luminol, and (iii) formation of the tert-butyl(per)oxyl adduct with the spin trap DMPO. NO. eliminated the signals of tyrosyl radical detected by ESR and oxoferryl detected by MS in the reaction of t-BuOOH with metMb. As evidenced by MS of apomyoglobin, this effect was due to the two-electron reduction of .Mb-FeIV = O by NO. at the oxoferryl center rather than to nitrosylation of the tyrosine residues. Results of our in vitro experiments suggest that NO. exhibits a potent, targetable antioxidant effect against oxidative damage produced by oxoferryl Mb/Hb.
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