过氧化氢使黄嘌呤氧化酶失活涉及定点羟基自由基的形成。

Inactivation of xanthine oxidase by hydrogen peroxide involves site-directed hydroxyl radical formation.

作者信息

Terada L S, Leff J A, Guidot D M, Willingham I R, Repine J E

机构信息

Webb-Waring Lung Institute, University of Colorado Health Sciences Center, Denver 80262.

出版信息

Free Radic Biol Med. 1991;10(1):61-8. doi: 10.1016/0891-5849(91)90022-u.

DOI:10.1016/0891-5849(91)90022-u

PMID:1646751

Abstract

The mechanism of xanthine oxidase (XO) inactivation by hydrogen peroxide (H2O2) and its biologic significance are unclear. We found that addition of increasing concentrations of H2O2 progressively decreased xanthine oxidase activity in the presence but not the absence of xanthine in vitro. Inactivation of XO by H2O2 was also enhanced by anaerobic reduction of XO by xanthine. Inactivation of XO by H2O2 was accompanied by production of hydroxyl radical (.OH), measured as formation of formaldehyde from dimethylsulfoxide (DMSO). In contrast, addition of H2O2 to deflavo XO did not produce .OH. Inactivation of XO by H2O2 was decreased by simultaneous addition of the .OH scavenger, DMSO. However, inactivation of XO by H2O2 and formation of .OH were not decreased following addition of the metal chelator. DETAPAC, and/or the O2 scavenger, superoxide dismutase. The results suggest that inactivation of XO by H2O2 occurs by production of .OH following direct reduction of H2O2 by XO at the flavin site.

摘要

过氧化氢（H₂O₂）使黄嘌呤氧化酶（XO）失活的机制及其生物学意义尚不清楚。我们发现，在体外有黄嘌呤存在而不是不存在黄嘌呤的情况下，添加浓度不断增加的H₂O₂会逐渐降低黄嘌呤氧化酶的活性。黄嘌呤对XO进行厌氧还原也会增强H₂O₂对XO的失活作用。H₂O₂使XO失活的过程伴随着羟自由基（·OH）的产生，这通过二甲基亚砜（DMSO）生成甲醛来测定。相比之下，向脱辅基XO中添加H₂O₂不会产生·OH。同时添加·OH清除剂DMSO会降低H₂O₂对XO的失活作用。然而，添加金属螯合剂DETAPAC和/或O₂清除剂超氧化物歧化酶后，H₂O₂对XO的失活作用和·OH的形成并未降低。结果表明，H₂O₂使XO失活是通过XO在黄素位点直接还原H₂O₂后产生·OH来实现的。