Reactivation studies of an affinity labeled steroid oxido-reductase. I. Inactivation of 20 beta-hydroxysteroid dehydrogenase with 6 beta-bromoacetoxyprogesterone vs 6 beta-bromoprogesterone.

20 beta-Hydroxysteroid dehydrogenase (E.C. 1.1.1.53), which had been completely inactivated with 6beta-bromoacetoxyprogesterone at pH 7.0, was reactivated by elevating the pH. The rate of reactivation is pH dependant, characteristic of base-catalysed ester hydrolysis. Similar experiments with 6beta-bromoprogesterone fail to produce reactivation of the affinity labeled enzyme. Formation and scission of different types of covalent bonds during affinity labeling and reactivation attempts accounts for the different result obtained with each steroid. The activity of the reactivated steroid oxido-reductase vs the native enzyme, and also substrate stabilization of the enzyme are discussed.