GST trimers transfer GS from GSH to luminal substrates

The microsomal glutathione S-transferases (MGSTs) catalyse the nucleophilic attack by reduced glutathione (GSH) on nonpolar compounds that contain an electrophilic C, N, or S atom. Three major families of proteins are widely distributed in nature. The cytosolic and mitochondrial GST families comprise soluble enzymes that are only distantly related whilst the third family comprises microsomal GST, referred to as membrane-associated proteins in eicosanoid and glutathione (MAPEG) metabolism. Three members of this family function as detoxification enzymes, MGST1-3 (DeJong et al. 1988, Kelner et al. 1996, Jakobsson et al. 1996, Jakobsson et al. 1997). Electron crystallography studies in rat Mgst1 indicate these enzymes function as homotrimers (Holm et al. 2002). Both aflatoxin B1 exo- and endo-epoxides (AFXBO and AFNBO) conjugate with glutathione. These conjugates are eventually excreted in urine as mercapturic acids.

微囊体谷胱甘肽S-转移酶（MGSTs）催化还原型谷胱甘肽（GSH）对含有亲电性C、N或S原子的非极性化合物的亲核攻击。在自然界中广泛分布的三大蛋白质家族。细胞质和线粒体GST家族包含可溶性酶，二者关系较为疏远，而第三家族则包含微囊体GST，亦称为二十碳烯酸和谷胱甘肽（MAPEG）代谢中的膜结合蛋白。该家族中的三个成员作为解毒酶发挥作用，分别为MGST1-3（DeJong等，1988；Kelner等，1996；Jakobsson等，1996；Jakobsson等，1997）。对大鼠Mgst1的电子晶体学研究表明，这些酶以同源三聚体的形式存在（Holm等，2002）。黄曲霉毒素B1的外-和内-环氧物（AFXBO和AFNBO）与谷胱甘肽结合。这些结合物最终以牛磺酸的形式通过尿液排出。