title: 5 alpha,6 alpha-Epoxy-cholestan-3 beta-ol (cholesterol alpha-oxide): A specific substrate for rat liver glutathione transferase B.
abstract: A semi-micro assay was developed for the conjugation of 5 alpha,6 alpha-epoxy-cholestan-3 beta-ol (cholesterol alpha-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 4 microM cholesterol alpha-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 (approximately 100 pmol . min-1 . 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.
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D051381:Rats
chemical_list: D007527:Isoenzymes; C002415:cholesterol alpha-oxide; D002784:Cholesterol; D005982:Glutathione Transferase