Pierce S, Tappel A L
Biochim Biophys Acta. 1978 Mar 14;523(1):27-36. doi: 10.1016/0005-2744(78)90005-0.
There are two enzymes in rat liver with glutathione peroxidase activity when cumene hydroperoxide is used as substrate. One is the selenium-requiring glutathione peroxidase (glutathione:hydrogen-peroxide oxidoreductase, EC 1.11.1.9) and the other appears to be independent of dietary selenium. Activities of the two enzymes vary greatly among tissues and among animals. The molecular weight of the enzyme with selenium-independent glutathione peroxidase activity was estimated by gel filtration to be 35 000, and the subunit molecular weight was estimated by dodecyl sulfate-polyacrylamide gel electrophoresis to be 17 000. Double reciprocal plots of enzyme activity as a function of substrate concentration produced intersecting lines which are suggestive of a sequential reaction mechanism. The Km for glutathione was 0.20 mM and the Km for cumene hydroperoxide was 0.57 mM. The enzyme was inhibited by N-ethylmaleimide, but not by iodoacetic acid. Inhibition by cyanide was competitive with respect to glutathione and the Ki for cyanide was 0.95 mM. This selenium-independent glutathione peroxidase also catalyzes the conjugation of glutathione to 1-chloro-2,4-dinitrobenzene. Along with other similarities to glutathione S-transferase, this suggests that the selenium-independent glutathione peroxidase and glutathione S-transferase activities in rat liver are of the same enzyme.
当以氢过氧化异丙苯作为底物时，大鼠肝脏中有两种具有谷胱甘肽过氧化物酶活性的酶。一种是需要硒的谷胱甘肽过氧化物酶（谷胱甘肽：过氧化氢氧化还原酶，EC 1.11.1.9），另一种似乎与膳食硒无关。这两种酶的活性在不同组织和不同动物之间差异很大。通过凝胶过滤估计，具有不依赖硒的谷胱甘肽过氧化物酶活性的酶的分子量为35000，通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳估计其亚基分子量为17000。酶活性作为底物浓度函数的双倒数图产生相交线，这表明是一种顺序反应机制。谷胱甘肽的Km为0.20 mM，氢过氧化异丙苯的Km为0.57 mM。该酶被N-乙基马来酰亚胺抑制，但不被碘乙酸抑制。氰化物的抑制作用在谷胱甘肽方面是竞争性的，氰化物的Ki为0.95 mM。这种不依赖硒的谷胱甘肽过氧化物酶还催化谷胱甘肽与1-氯-2,4-二硝基苯的结合。连同与谷胱甘肽S-转移酶的其他相似之处，这表明大鼠肝脏中不依赖硒的谷胱甘肽过氧化物酶和谷胱甘肽S-转移酶活性是同一种酶。
