Role of reduced glutathione in the delta(5)-3-kitosteroid isomerase reaction of liver. |
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Authors: | A M Benson P Talalay |
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Affiliation: | Department of Pharmacology and Experimental Therapeutics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A. |
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Abstract: | Partially purified rat liver Δ5-3-ketosteroid isomerase (EC 5.3.3.1) is profoundly and specifically activated by reduced glutathione (GSH). This stimulating effect shows normal saturating kinetics, and both Km and Vmax are pH-dependent. The binding of GSH is independent of the concentration of Δ5-androstene-3,17-dione, whereas the Km for Δ5-androstene-3,17-dione is markedly reduced by saturating levels of GSH. The same catalytic site appears to isomerize both Δ5-androstene-3,17-dione and Δ5-pregnene-3,20-dione. Several steroidal inhibitors compete with Δ5-androstene-3,17-dione, whereas -methyl-glutathione competes with GSH. This activation of Δ5-3-ketosteroid isomerase is also observed in the livers of other species (calf, guinea pig, human), and represents a hitherto unrecognized function of reduced glutathione. |
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Keywords: | GSH reduced glutathione DTT dithiothreitol isomerase |
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