Awasthi Y C, Dao D D
Placenta Suppl. 1981;3:289-301.
Glutathione peroxidase and GSH S-transferases play significant physiological roles in the detoxification mechanisms. The present study indicates that only selenium-dependent GSH-peroxidase I is present in human placenta. GSH-peroxidase II (non-selenium GSH-peroxidase) is totally absent from this tissue. The placental GSH-peroxidase has a relative molecular mass of 85 000 and is a tetramer of equal-size subunits. It is cyanide sensitive and its properties are similar to those of human erythrocyte GSH-peroxidase. In contrast to human liver, which has seven GSH S-transferases, the placenta has only one species of GSH S-transferase. This enzyme (pI 4.5, relative molecular mass 45 000, subunit size 22 500) has a different amino acid composition from that of liver and erythrocyte GSH S-transferases. From immunological studies, the placental GSH S-transferase appears also to have a genetic origin distinct from that of liver, erythrocyte and kidney GSH S-transferases. The placental GSH S-transferase does not express GSH-peroxidase activity. The overall substrate specificities of placental GSH S-transferase are also narrow, compared with liver enzymes. The present study indicates that, although these two GSH-linked detoxification mechanisms are operative in placenta, they appear to be less efficient than the similar mechanisms operating in liver.
谷胱甘肽过氧化物酶和谷胱甘肽S-转移酶在解毒机制中发挥着重要的生理作用。本研究表明，人胎盘中仅存在硒依赖性谷胱甘肽过氧化物酶I。该组织中完全不存在谷胱甘肽过氧化物酶II（非硒依赖性谷胱甘肽过氧化物酶）。胎盘谷胱甘肽过氧化物酶的相对分子质量为85000，是由等大小亚基组成的四聚体。它对氰化物敏感，其性质与人类红细胞谷胱甘肽过氧化物酶相似。与具有七种谷胱甘肽S-转移酶的人类肝脏不同，胎盘仅有一种谷胱甘肽S-转移酶。这种酶（pI 4.5，相对分子质量45000，亚基大小22500）的氨基酸组成与肝脏和红细胞谷胱甘肽S-转移酶不同。从免疫学研究来看，胎盘谷胱甘肽S-转移酶似乎也有与肝脏、红细胞和肾脏谷胱甘肽S-转移酶不同的遗传起源。胎盘谷胱甘肽S-转移酶不表现出谷胱甘肽过氧化物酶活性。与肝脏中的酶相比，胎盘谷胱甘肽S-转移酶的总体底物特异性也较窄。本研究表明，尽管这两种与谷胱甘肽相关的解毒机制在胎盘中起作用，但它们似乎不如在肝脏中起作用的类似机制有效。
