Awasthi S, Singhal S S, Srivastava S K, Awasthi Y C
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77555.
Arch Biochem Biophys. 1993 Feb 15;301(1):143-50. doi: 10.1006/abbi.1993.1126.
Recent studies have indicated that sex hormones may regulate expression of murine glutathione S-transferase (GST) isozymes. Therefore, we have purified and compared GST isozymes of murine ovary and testis, two tissues with markedly different hormonal milieu. Isoelectric profiles of the GST isozymes of both these tissues were found to be closely similar. Both expressed one alpha-class GST (pI9.8), one pi-class GST (pI8.9), and three mu-class GSTs (pI8.5, 7.9, and 6.7). In addition, an isozyme (pI5.8) corresponding to the rat GST 8-8 was also expressed in both these tissues. Total GST protein/g tissue was about 1.7-fold more abundant in testis. The specific activities of the cationic isozymes of testis were 1.2- to 2.4-fold higher as compared to those of ovaries. On the other hand, the specific activities of the anionic testicular isozymes were 6.4- to 10-fold higher compared to the corresponding ovarian isozymes. Structural properties including the N-terminal sequences of the testicular isozymes were indistinguishable from those of their ovarian counterparts. The N-terminal sequence of the pi-class GST of both tissues was similar to that of mouse liver GST pi. The three mu-class GSTs of testis and ovary arise from the dimeric combinations of two subunits whose N-terminal sequences determined up to 24 residues were similar to those of mouse liver GST subunits mu 1 and mu 2. Although testicular and ovarian isozymes were structurally similar, Kcat values of some of the testicular isozymes were up to 10-fold higher than those of the corresponding ovarian isozymes. The substrate specificities were also significantly different for the corresponding isozymes of testis and ovary.
近期研究表明，性激素可能调节小鼠谷胱甘肽S-转移酶（GST）同工酶的表达。因此，我们纯化并比较了小鼠卵巢和睾丸的GST同工酶，这两个组织具有明显不同的激素环境。发现这两种组织的GST同工酶的等电图谱非常相似。两者均表达一种α类GST（pI9.8）、一种π类GST（pI8.9）和三种μ类GST（pI8.5、7.9和6.7）。此外，在这两种组织中还表达了一种与大鼠GST 8-8相对应的同工酶（pI5.8）。睾丸中每克组织的总GST蛋白含量比卵巢约高1.7倍。睾丸阳离子同工酶的比活性比卵巢的高1.2至2.4倍。另一方面，睾丸阴离子同工酶的比活性比相应的卵巢同工酶高6.4至10倍。包括睾丸同工酶N端序列在内的结构特性与其卵巢对应物无法区分。两种组织的π类GST的N端序列与小鼠肝脏GSTπ的相似。睾丸和卵巢的三种μ类GST来自两个亚基的二聚体组合，其N端序列确定的多达24个残基与小鼠肝脏GST亚基μ1和μ2的相似。尽管睾丸和卵巢同工酶在结构上相似，但一些睾丸同工酶的Kcat值比相应的卵巢同工酶高10倍。睾丸和卵巢相应同工酶的底物特异性也有显著差异。
