The isomerization of Delta(5)-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 produ ct formation. Substitution of S-methylglutathione for glutathione gave a de crease in activity to a level lower than without glutathione and led to the conclusion that the sulfhydryl group is important for catalysis. The pH de pendencies of k(cat) and k(cat)/K-M values suggest that the thiolate of glu tathione acts as a base in the proton transfer of the catalyzed reaction (C ) 2001 Elsevier Science Ireland Ltd. All rights reserved.