Ahmad H, Singh S V, Medh R D, Ansari G A, Kurosky A, Awasthi Y C
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77550.
Arch Biochem Biophys. 1988 Nov 1;266(2):416-26. doi: 10.1016/0003-9861(88)90273-1.
Isozyme characterization of glutathione S-transferase (GST) isolated from bovine ocular tissue was undertaken. Two isozymes of lens, GST 7.4 and GST 5.6, were isolated and found to be homodimers of a Mr 23,500 subunit. Amino acid sequence analysis of a 20-residue region of the amino terminus was identical for both isozymes and was identical to GST psi and GST mu of human liver. Antibodies raised against GST psi cross-reacted with both lens isozymes. Although lens GST 5.6 and GST 7.4 demonstrated chemical and immunological relatedness, they were distinctly different as evidenced by their pI and comparative peptide fingerprint. A corneal isozyme, GST 7.2, was also isolated and established to be a homodimer of Mr 24,500 subunits. Sequence analysis of the amino-terminal region indicated it to be about 67% identical with the GST pi isozyme of human placenta. Antibodies raised against GST pi cross-reacted with cornea GST 7.2. Another corneal isozyme, GST 8.7, was found to be homodimer of Mr 27,000 subunits. Sequence analysis revealed it to have a blocked amino-terminus. GST 8.7 immunologically cross-reacted with the antibodies raised against cationic isozymes of human liver indicating it to be of the alpha class. Two isozymes of retina, GST 6.8 and GST 6.3, were isolated and identified to be heterodimers of subunits of Mr 23,500 and 24,500. Amino-terminal sequence analysis gave identical results for both retina GST 6.8 and GST 6.3. The sequence analysis of the Mr 23,500 subunit was identical to that obtained for lens GSTs. Similarly, sequence analysis of the Mr 24,500 subunit was identical to that obtained for the cornea GST 7.2 isozyme. Both the retina isozymes cross-reacted with antibodies raised against human GST psi as well as GST pi. The results of these studies indicated that all three major classes of GST isozymes were expressed in bovine eye but the GST genes were differentially expressed in lens, cornea, and retina. In lens only the mu class of GST was expressed, whereas cornea expressed alpha and pi classes and retina expressed mu and pi classes of GST isozymes.
对从牛眼组织中分离出的谷胱甘肽S-转移酶（GST）进行了同工酶特性分析。分离出晶状体的两种同工酶GST 7.4和GST 5.6，发现它们是Mr 23,500亚基的同型二聚体。两种同工酶氨基末端20个残基区域的氨基酸序列分析结果相同，且与人肝的GST psi和GST mu相同。针对GST psi产生的抗体与两种晶状体同工酶均发生交叉反应。尽管晶状体GST 5.6和GST 7.4表现出化学和免疫相关性，但它们的pI和比较肽指纹图谱表明它们明显不同。还分离出一种角膜同工酶GST 7.2，确定其为Mr 24,500亚基的同型二聚体。氨基末端区域的序列分析表明，它与人胎盘的GST pi同工酶约67%相同。针对GST pi产生的抗体与角膜GST 7.2发生交叉反应。另一种角膜同工酶GST 8.7被发现是Mr 27,000亚基的同型二聚体。序列分析显示其氨基末端被封闭。GST 8.7与针对人肝阳离子同工酶产生的抗体发生免疫交叉反应，表明它属于α类。分离出视网膜的两种同工酶GST 6.8和GST 6.3，确定它们是Mr 23,500和24,500亚基的异源二聚体。视网膜GST 6.8和GST 6.3的氨基末端序列分析结果相同。Mr 23,500亚基的序列分析结果与晶状体GST的序列分析结果相同。同样，Mr 24,500亚基的序列分析结果与角膜GST 7.2同工酶的序列分析结果相同。两种视网膜同工酶均与针对人GST psi和GST pi产生的抗体发生交叉反应。这些研究结果表明，GST同工酶的所有三大类均在牛眼中表达，但GST基因在晶状体、角膜和视网膜中差异表达。在晶状体中仅表达GST的mu类，而角膜表达GST同工酶的α类和pi类，视网膜表达GST同工酶的mu类和pi类。
