Expression of an abundant α-class glutathione S-transferase in bovine and human adrenal cortex tissues

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Abstract
Bovine adrenal cortex tissue expresses high levels of glutathione S-transferase (GST) from each of the α, μ and π gene families. We describe the purification and characterization of an abundant α-class GST from this tissue that has not been identified previously because of its failure to bind to S-hexylglutathione–Sepharose 6B (S-hexG-Ag). This enzyme has been affinity purified on glutathione–Sepharose 6B (GSH-Ag) and was obtained in a highly purified form by employing S-hexG-Ag to remove the bulk of GST before chromatography on GSH-Ag. The purified GST eluted from GSH-Ag was found to exhibit marked peroxidase and Δ5-ketosteroid isomerase activities (19·2 and 1·67 U/mg respectively). The bovine enzyme also showed high GST activity towards 4-hydroxynonenal (5·09 U/mg). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that the bovine GST contains two distinct polypeptides, one with an Mr of 25 900 and the other with an Mr of 26 500. An abundant α-class GST was also purified from human adrenal cortex that possessed properties which were similar to the bovine α-class GST described above; however, unlike the bovine enzyme, the corresponding human α-class GST bound to S-hexG-Ag. As with the bovine enzyme, the purified human GST displayed marked peroxidase and isomerase activities (27 and 4·02 U/mg respectively). Further analysis on SDS-PAGE (Mr 25 800) and reverse-phase highperformance liquid chromatography established that this abundant α-class GST in human adrenal cortex is equivalent to the human liver GST B1B1 enzyme. As both human and bovine adrenal cortex contain high levels of α-class GST with similar catalytic properties, we discuss the possible functions of these enzymes in this tissue. Journal of Endocrinology (1992) 132, 83–92

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