Dehydroepiandrosterone sulphate sulphoydrolase from human placenta microsomes-Properties of the purified enzyme

The purified DHEAS-ase revealed specific activity of 1520 nmol × min−1 × mg protein−1 and exhibited optimal activity at pH 8.4. The Km value was established to be 3.3 ± 0.07 × 10−5 M. The pI value was around 8.7. The molecular weight estimated by gel filtration was 7.4 kDa. The purified DHEAS-ase was not sensitive to the common sulphohydrolase inhibitors, such as phosphate, sulphate and sulphide ions, but was inhibited by several phosphohydrolase inhibitors (ammonium molybdate, vanadium oxide(V), zinc acetate). Steroids effected inhibition or activation of the purified enzyme. The data concerning substances reacting with -SH groups suggest that in the physiological conditions DHEAS-ase is controlled by the redox status of the cell.