Human Placental Steroid-Sulfatase Solubilized with a Cholic-Acid Derivative: Molecular Mass, Kinetic Properties and Susceptibility to Glycosidases

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Abstract
Human placental steroid-sulfatase was extracted nearly quantitatively from microsomes as well as from acetone dry powder of placenta homogenates using CHAPS [3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate] as detergent. The solubilized enzyme was enriched 10-fold by ammonium sulfate precipitation and gel chromatography. The sulfatase extracted from both microsomes and acetone dry powder eluted as a single fraction on Sepharose 6B, but with different apparent MW (390 and 270 kDa [Kilodaltons], respectively). Kinetic experiments with the sulfate esters of dehydroepiandrosterone, 16.alpha.-hydroxydehydroepiandrosterone, esterone and estriol as substrates or inhibitors indicated that the solubilized sulfatase was fully active. Both the particulate and the extracted enzyme showed higher affinities for the 16-unsubstituted than for the 16.alpha.-hydroxylated substrates. A competitive inhibition was observed in mixed substrate incubations with dehydroepiandrosterone sulfate/16.alpha.-hydroxydehydroepiandrosterone sulfate and estrone sulfate/estriol sulfate, diverse patterns of inhibition were obtained with dehydroepiandrosterone sulfate/estrone sulfate, depending on the sulfatase preparation used. Evidence for the distinct nature of the steroid-sulfatase and the estrogen-sulfatase was not obtained.

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