SUBSTRATE-INHIBITION OF XANTHINE-OXIDASE AND ITS INFLUENCE ON SUPEROXIDE RADICAL PRODUCTION

被引：34

作者：

RUBBO, H ^{[1
]}

RADI, R ^{[1
]}

PRODANOV, E ^{[1
]}

机构：

[1] UNIV REPUBL MONTEVIDEO,FAC MED,DEPT BIOQUIM,AV GRAL FLORES 2125,MONTEVIDEO 11800,URUGUAY

来源：

BIOCHIMICA ET BIOPHYSICA ACTA | 1991年 / 1074卷 / 03期

关键词：

XANTHINE OXIDASE; SUPEROXIDE; HYPOXANTHINE; XANTHINE; URIC ACID; INHIBITION;

D O I：

10.1016/0304-4165(91)90089-Y

中图分类号：

Q5 [生物化学]; Q7 [分子生物学];

学科分类号：

071010 ; 081704 ;

摘要：

The influence of substrate inhibition on xanthine oxidase-intramolecular electron transport was studied by steady-state kinetic analysis. Experiments with hypoxanthine and xanthine up to 900-mu-M indicated an inhibition pattern which fitted an equation of the general form upsilon-0 = upsilon-max . [S]/(K(m) + a[S] + b[S]2/K(i)). Univalent electron flux to oxygen was favored at substrate concentrations above 50-mu-M. This augmentation of univalent flux percentage that appeared at a high substrate concentration was greater for hypoxanthine than xanthine and at pH 8.3 than at 9.5. Our results support a mechanism of inhibition in which a substrate-reduced enzyme, non-productive Michaelis complex was formed. It is possible that this non-productive complex favored the univalent pathway of enzyme reoxidation (superoxide production) by increasing the midpoint redox potential of the molybdenum active site.

引用

页码：386 / 391

页数：6

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