牛红细胞谷胱甘肽过氧化物酶脱氢抗坏血酸还原酶和硫醇转移酶（谷氧还蛋白）活性的鉴定

Identification of the dehydroascorbic acid reductase and thioltransferase (Glutaredoxin) activities of bovine erythrocyte glutathione peroxidase.

作者信息

Washburn M P, Wells W W

机构信息

Department of Biochemistry, Michigan State University, East Lansing, Michigan, 48824, USA.

出版信息

Biochem Biophys Res Commun. 1999 Apr 13;257(2):567-71. doi: 10.1006/bbrc.1999.0508.

DOI:10.1006/bbrc.1999.0508

PMID:10198252

Abstract

Bovine erythrocyte glutathione (GSH) peroxidase (GPX, EC 1.11.1.9) was examined for GSH-dependent dehydroascorbate (DHA) reductase (EC 1.8.5.1) and thioltransferase (EC 1.8.4.1) activities. Using the direct assay method for GSH-dependent DHA reductase activity, GPX had a kcat (app) of 140 +/- 9 min-1 and specificity constants (kcat/Km(app)) of 5.74 +/- 0.78 x 10(2) M-1s-1 for DHA and 1.18 +/- 0.17 x 10(3) M-1s-1 for GSH based on the monomer Mr of 22,612. Using the coupled assay method for thioltransferase activity, GPX had a kcat (app) of 186 +/- 9 min-1 and specificity constants (app) of 1. 49 +/- 0.14 x 10(3) M-1s-1 for S-sulfocysteine and 1.51 +/- 0.18 x 10(3) M-1s-1 for GSH based on the GPX monomer molecular weight. GPX has a higher specificity constant for S-sulfocysteine than DHA, and both assay systems gave nearly identical specificity constants for GSH. The DHA reductase and thioltransferase activities of GPX adds to the repertoire of functions of this enzyme as an important protector against cellular oxidative stress.

摘要

对牛红细胞谷胱甘肽（GSH）过氧化物酶（GPX，EC 1.11.1.9）进行了谷胱甘肽依赖性脱氢抗坏血酸（DHA）还原酶（EC 1.8.5.1）和硫醇转移酶（EC 1.8.4.1）活性检测。采用谷胱甘肽依赖性DHA还原酶活性的直接检测方法，基于22,612的单体相对分子质量，GPX对DHA的催化常数（表观）为140±9 min⁻¹，特异性常数（kcat/Km（表观））为5.74±0.78×10² M⁻¹s⁻¹，对GSH的特异性常数为1.18±0.17×10³ M⁻¹s⁻¹。采用硫醇转移酶活性的偶联检测方法，基于GPX单体分子量，GPX对S-磺基半胱氨酸的催化常数（表观）为186±9 min⁻¹，特异性常数（表观）为1.49±0.14×10³ M⁻¹s⁻¹，对GSH的特异性常数为1.51±0.18×10³ M⁻¹s⁻¹。GPX对S-磺基半胱氨酸的特异性常数高于对DHA的特异性常数，并且两种检测系统对GSH给出的特异性常数几乎相同。GPX的DHA还原酶和硫醇转移酶活性增加了该酶作为细胞氧化应激重要保护剂的功能范围。