Hydrolysis of deoxycorticosterone-21-yl sulphate and dehydroepiandrosterone sulphate by microsomal preparations of human placentae: evidence for a common enzyme.
The human placenta can hydrolyse both dehydroepiandrosterone-3 beta-yl sulphate (DHASO4-) and deoxycorticosterone-21-yl sulphate (DOCSO4-). There is some uncertainty as to whether the same or different enzymes are responsible for hydrolysis of these substrates. As a fresh approach to this problem we have compared the quantities of DHASO4- and DOCSO4- hydrolysed by microsomal preparations of placentae obtained from 14 normal pregnancies and from 14 pregnancies complicated by steroid sulphatase deficiency. Under the conditions used, and standardizing the results to unit time and quantity of protein, 1380-8830 fmol DHASO4- were hydrolysed by 14 normal placentae whereas less than 1000 fmol DHASO4- were hydrolysed by the other 14 placentae, thereby designated as steroid sulphatase deficient. Net hydrolysis of DOCSO4- by the preparations of normal tissue was 9-52 fmol; hydrolysis of this substrate by steroid sulphatase-deficient tissues was indistinguishable from that by boiled tissue (less than 29 fmol). Thus preparations of placentae which hydrolysed DHASO4- also hydrolysed DOCSO4-; tissues which did not hydrolyse DHASO4- also failed to hydrolyse DOCSO4-. The quantities of DHASO4- and DOCSO4- hydrolysed by the 28 individual placentae showed a positive correlation (r = 0.91, P less than 0.001). The apparent Michaelis constants for hydrolysis of DHASO4- and DOCSO4- were 38 and 274 mumol/l respectively. These results are consistent with the proposal that these substrates are hydrolysed by a common enzyme.