Hussey A J, Hayes J D
University Department of Clinical Biochemistry, Royal Infirmary, Edinburgh, UK.
Biochim Biophys Acta. 1993 Nov 10;1203(1):131-41. doi: 10.1016/0167-4838(93)90047-u.
The major human Mu-class glutathione S-transferases (GST) have been purified to allow comparisons of their catalytic, physicochemical and immunochemical properties. GST isoenzymes, purified from hepatic, testicular and skeletal muscle tissue were found to comprise three distinct subunits (M1, M2 and M3) which may combine to form both homodimeric and heterodimeric proteins. Two distinct subunits, M1a and M1b, which represent allelic charge variants have been isolated but no polymorphic forms encoded at the GST M2 and M3 loci have been observed. Three GST isoenzymes (M1a-1a, M1a-1b and M1b-1b) have been purified from a single liver specimen. In addition, GST M1a-2, M1b-2, M2-2 and M2-3 have been isolated from muscle, whilst the M3-3 homodimer has been purified from human testis. The homodimeric enzymes GST M1a-1a, M1b-1b, M2-2 and M3-3 have pI values of 6.1, 5.5, 5.3 and 5.0, whilst SDS-PAGE indicated that M1a, M1b, M2 and M3 have molecular masses of 26.7, 26.6, 26.0 and 26.3 kDa, respectively. The M1, M2 and M3 subunits isolated from either liver, skeletal muscle or testis, are catalytically distinct. Both M1-type subunits (M1a and M1b) possess a high activity for trans-4-phenyl-3-buten-2-one, whereas, the skeletal muscle subunit M2 has a high activity towards 1,2-dichloro-4-nitrobenzene. By contrast, the testicular GST subunit M3 has no detectable activity towards either of these substrates. However, all three Mu-class subunits are active towards the compounds 4-hydroxynonenal and 4-hydroxydecinal, possible endogenous substrates which are produced by lipid peroxidation. The human Mu-class subunits can be distinguished immunochemically; antisera raised against the testicular GST M3-3 showed no reactivity towards either the M1 or M2 subunits. The M3 subunit has a blocked N-terminus but automated amino-acid sequencing of a CNBr-derived peptide allowed 14 residues of the M3 subunit to be identified. These data indicated that testicular GST M3-3 is likely to correspond to the brain/testis Mu-class GST cDNA described by Campbell et al. (Campbell E., Takahashi Y., Abramovitz M., Peretz M., & Listowsky I. (1990) J. Biol. Chem. 265, 9188-9193).
主要的人类Mu类谷胱甘肽S-转移酶（GST）已被纯化，以便比较它们的催化、物理化学和免疫化学性质。从肝脏、睾丸和骨骼肌组织中纯化的GST同工酶被发现由三个不同的亚基（M1、M2和M3）组成，它们可以结合形成同二聚体和异二聚体蛋白。已经分离出代表等位基因电荷变体的两个不同亚基M1a和M1b，但未观察到在GST M2和M3基因座编码的多态形式。已从单个肝脏标本中纯化出三种GST同工酶（M1a-1a、M1a-1b和M1b-1b）。此外，已从肌肉中分离出GST M1a-2、M1b-2、M2-2和M2-3，而M3-3同二聚体已从人类睾丸中纯化出来。同二聚体酶GST M1a-1a、M1b-1b、M2-2和M3-3的pI值分别为6.1、5.5、5.3和5.0，而SDS-PAGE表明M1a、M1b、M2和M3的分子量分别为26.7、26.6、26.0和26.3 kDa。从肝脏、骨骼肌或睾丸中分离出的M1、M2和M3亚基在催化上是不同的。两种M1型亚基（M1a和M1b）对反式-4-苯基-3-丁烯-2-酮具有高活性，而骨骼肌亚基M2对1,2-二氯-4-硝基苯具有高活性。相比之下，睾丸GST亚基M3对这两种底物中的任何一种都没有可检测到的活性。然而，所有三种Mu类亚基对化合物4-羟基壬烯醛和4-羟基癸醛都有活性，这两种化合物可能是脂质过氧化产生的内源性底物。人类Mu类亚基可以通过免疫化学方法区分；针对睾丸GST M3-3产生的抗血清对M1或M2亚基均无反应性。M3亚基的N末端被封闭，但对来自溴化氰衍生肽的自动氨基酸测序允许鉴定M3亚基的14个残基。这些数据表明，睾丸GST M3-3可能与Campbell等人描述的脑/睾丸Mu类GST cDNA相对应（Campbell E., Takahashi Y., Abramovitz M., Peretz M., & Listowsky I. (1990) J. Biol. Chem. 265, 9188-9193）。
