Lai H C, Tu C P
J Biol Chem. 1986 Oct 15;261(29):13793-9.
High multiplicity of GSH S-transferases (GST) with overlapping substrate specificities may be essential to their multiple roles in xenobiotics metabolism, drug biotransformation, and protection against peroxidative damage. Subunit composition analysis of rat liver GSH S-transferases indicated that heterodimer associations were not random, limiting the generation of GST isozyme multiplicity. We have analyzed a Yb subunit cDNA clone, pGTR187, that may correspond to an anionic Yb subunit sequence. Comparison with other GSH S-transferase cDNA sequences and blot hybridization results indicates that the multiple Yb subunits are encoded by a multigene family. This Yb subunit sequence has very limited homology to Ya and Yc subunit cDNAs, but slightly more sequence homology to the Yp subunit cDNA. More consistent sequence homology is found at the amino acid level with 28% conservation throughout the coding sequences. These results and results published from other laboratories clearly indicate that rat GSH S-transferases are products of at least four different gene families that constitute a supergene family. Conceptually, the supergene family may encode GSH S-transferases of very different structures that are essential to metabolize a multitude of xenobiotics in addition to serving other physiologically important functions.
谷胱甘肽S-转移酶（GST）具有多种重叠的底物特异性，这对于它们在异源生物代谢、药物生物转化以及防止过氧化损伤中的多种作用可能至关重要。大鼠肝脏谷胱甘肽S-转移酶的亚基组成分析表明，异二聚体的结合并非随机，限制了GST同工酶多样性的产生。我们分析了一个Yb亚基cDNA克隆pGTR187，它可能对应于阴离子Yb亚基序列。与其他谷胱甘肽S-转移酶cDNA序列的比较以及印迹杂交结果表明，多个Yb亚基由一个多基因家族编码。该Yb亚基序列与Ya和Yc亚基cDNA的同源性非常有限，但与Yp亚基cDNA的序列同源性略高。在氨基酸水平上发现了更一致的序列同源性，整个编码序列的保守性为28%。这些结果以及其他实验室发表的结果清楚地表明，大鼠谷胱甘肽S-转移酶是至少四个不同基因家族的产物，这些基因家族构成了一个超基因家族。从概念上讲，这个超基因家族可能编码结构非常不同的谷胱甘肽S-转移酶，这些酶除了发挥其他重要的生理功能外，对于代谢多种异源生物也是必不可少的。
