5α,6α‐Epoxy‐cholestan‐3β‐ol (cholesterol α‐oxide): A specific substrate for rat liver glutathione transferase B
- 27 December 1982
- journal article
- Published by Wiley in FEBS Letters
- Vol. 150 (2) , 499-502
- https://doi.org/10.1016/0014-5793(82)80798-9
Abstract
A semi-micro assay was developed for the conjugation of 5α,6α-epoxy-cholestan-3β-ol (cholesterol α-oxide) with glutathione. The soluble supernatant of rat liver homogenate catalysed the reaction at a rate of 0.2–0.5 pmol.min−1 .mg protein−1 with 4μM cholesterol α-oxide, while the reaction in the presence of GSH alone was barely detectable. Enzymic activity in the soluble supernatant was due equally to the two forms of glutathione transferase B (∼100 pmol.min−.mg protein−1), glutathione transferases AA, A, C and E being unreactive. The activity of purified glutathione transferase B was about 5-times that expected from the activity of the soluble supernatant. Complex enzyme kinetics were obtained suggestive of substrate inhibition.Keywords
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