Ishikawa T, Milbert U, Oesch F, Sies H
Eur J Biochem. 1986 Jan 15;154(2):299-305. doi: 10.1111/j.1432-1033.1986.tb09397.x.
A major isozyme of rat heart glutathione transferase was purified to homogeneity by Sephadex G-200 gel filtration, ammonium sulfate precipitation, CM-cellulose chromatography and affinity chromatography on S-hexylglutathione-linked Sepharose 6B. The purified isozyme was a dimer with an apparent relative molecular mass of 50 000 composed of two Yb-size subunits (Mr = 26 500). The isozyme is immunologically related to rat liver glutathione transferase X and 3-3, especially closely to transferase X, and no immunological cross-reactivity with subunits 1 and 2 of hepatic glutathione transferases was observed. The isoelectric point (pI = 6.9) of the isozyme was identical with and the substrate specificity was very similar to transferase X. Thus, the cardiac near-neutral isozyme is considered to be identical to glutathione transferase X recognized in rat liver. The amount of this near-neutral isozyme estimated to be present in heart tissue is 70 micrograms/g. The isozyme has relatively high activities towards alpha, beta-unsaturated carbonyl compounds such as trans-4-phenyl-3-buten-2-one and trans-4-hydroxynon-2-enal. The latter is a cytotoxic product resulting from lipid peroxidation of polyunsaturated fatty acids, and the cardiac isozyme may play a physiologically significant role with glutathione conjugation of this compound. In addition to the near-neutral isozyme, acidic forms with isoelectric points of 4.9, 5.2 and 5.5 were partially purified; some of them are considered to consist of subunits immunologically related to transferase X.
通过Sephadex G - 200凝胶过滤、硫酸铵沉淀、CM - 纤维素色谱以及在S - 己基谷胱甘肽连接的琼脂糖6B上进行亲和色谱，将大鼠心脏谷胱甘肽转移酶的一种主要同工酶纯化至同质。纯化的同工酶是一种二聚体，表观相对分子质量为50000，由两个Yb大小的亚基组成（Mr = 26500）。该同工酶与大鼠肝脏谷胱甘肽转移酶X和3 - 3在免疫上相关，尤其与转移酶X密切相关，并且未观察到与肝脏谷胱甘肽转移酶亚基1和2的免疫交叉反应。该同工酶的等电点（pI = 6.9）与转移酶X相同，底物特异性也非常相似。因此，心脏近中性同工酶被认为与在大鼠肝脏中识别的谷胱甘肽转移酶X相同。估计心脏组织中存在的这种近中性同工酶的量为70微克/克。该同工酶对α，β - 不饱和羰基化合物如反式 - 4 - 苯基 - 3 - 丁烯 - 2 - 酮和反式 - 4 - 羟基壬 - 2 - 烯醛具有相对较高的活性。后者是多不饱和脂肪酸脂质过氧化产生的细胞毒性产物，心脏同工酶可能在该化合物与谷胱甘肽结合中发挥生理上重要的作用。除了近中性同工酶外，还部分纯化了等电点为4.9、5.2和5.5的酸性形式；其中一些被认为由与转移酶X免疫相关的亚基组成。
