The isomerization of Δ5-androstene-3,17-dione catalyzed by human glutathione transferase A1-1

Human glutathione transferase A1-1 can catalyze the isomerization of Delta (5)-androstene-3,17-dione to its isomer in the absence of glutathione. The presence of glutathione, however, significantly increases the rate of product formation. Substitution of S-methylglutathione for glutathione gave a decrease in activity to a level lower than without glutathione and led to the conclusion that the sulfhydryl group is important for catalysis. The pH dependencies of k(cat) and k(cat)/K-M values suggest that the thiolate of glutathione acts as a base in the proton transfer of the catalyzed reaction (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.