1. Dehydroepiandrosterone sulphate was hydrolysed by human placental steroid 3β-sulphatase in H218O. Equimolar amounts of dehydroepiandrosterone and sodium sulphate were similarly incubated as controls. After incubation, unconjugated steroid was extracted with ether and sulphate precipitated as barium sulphate. Both were analysed for 18O-content by mass spectroscopy, the sulphate as carbon dioxide after initial pyrolysis with graphite. 2. In duplicate experiments, amounts of 18O equivalent to 67% and 72% respectively of the theoretical content calculated for rupture of the O–S bond were present in the sulphate. As the enzyme preparation used was a microsomal preparation containing unenriched endogenous sulphate and phosphate, and as no incorporation of isotope was found in the steroid, it is concluded that the placental enzyme effects hydrolysis by rupture of the O–S bond.
- © 1969 The Biochemical Society