Pergamon ft. Steroid Biochem. Molec. Biol. Vol. 50, No. 1/2, pp. 101-104, 1994 Copyright © 1994 Elsevier Science Ltd 0960-0760(94)E0072-S Printed in Great Britain. All rights reserved 0960-0760/94 $7.00 + 0.00 Rapid Communication The Hydrolysis of Oestrone Sulphate and Dehydroepiandrosterone Sulphate by Human Steroid Sulphatase Expressed in Transfected COS-1 Cells A. Purohit, 1 Sophie Dauvois, 2 M. G. Parker, 2 B. V. L. Potter, 3 G. J. Williams 3 and M. J. Reed t* 1Unit of Metabolic Medicine, St Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London W2 1PG, 2Molecular Endocrinology Laboratory, Imperial Cancer Research Fund, Lincoln's Inn Fields, London WC2A 3PX and 3School of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, Avon BA2 7A Y, England Whether the same or distinct steroid sulphatases (STS) are involved in the hydrolysis of alkyl and aryl steroid sulphates remains controversial. We have examined the ability of a placental steroid sulphatase to hydrolyse oestrone sulphate and/or dehydroepiandrosterone sulphate (DHA-S) by expressing the enzyme in COS-1 cells. Using either intact cells or broken cell preparations, the expressed sulphatase was found to hydrolyse both oestrone sulphate and DHA-S. The catalysis of oestrone sulphate and DHA-S by the expressed sulphatase was almost completely abolished by the steroid sulphatase inhibitor, oestrone-3-O-sulphamate. It is concluded that both alkyl and aryl steroid sulphates can be hydrolysed by the same steroid sulphatase. ft. Steroid Biochem. Molec. Biol., Vol. 50, No. 1/2, pp. 101-104, 1994 Steroid sulphates are important intermediates in the synthesis, transport and action of steroid hormones [1-4]. Conversion of oestrone sulphate to oestrone, and of dehydroepiandrosterone sulphate (DHA-S) to DHA, is thought to be an important source of biologi- cally active steroids [5, 6]. Although the hydrolysis of DHA-S and oestrone sulphate involves the removal of a sulphate group, whether the hydrolysis of these conjugates is mediated by the same or different sul- phatases remains controversial [7]. Mammalian aryl sulphatases are classified into three types: A, B and C. The microsomal aryl sulphatase C (steryl sulphate sulphohydrolase, EC 3.1.6.2.), which is responsible for the hydrolysis of sulphate esters of 3fl-hydroxysteroids, has been purified using many different solubilization and isolation procedures. Using purified enzyme prep- arations, evidence has been reported to support the *Correspondence to M. J. Reed. Received 7 Dec. 1993; accepted 17 Mar. 1994. existence of distinct sulphatases for the hydrolysis of oestrone sulphate and DHA-S [8], and that the sul- phatases hydrolysing oestrone sulphate and DHA-S are in fact the same enzyme [9, 10]. In addition, investigations of the physico-chemical or kinetic characteristics of steroid sulphatases in microsomal preparations of breast tumours or breast cancer cells have suggested that the same or distinct enzymes are responsible for the catalysis of oestrone sulphate and DHA-S [11-13]. A 2.4 kb cDNA for human placental steroid sulphatase has now been isolated, sequenced and shown to encode an enzymatically active protein [14, 15]. In this study we have transiently transfected this placental steroid sulphatase DNA into COS-1 cells and examined the ability of the expressed sulphatase to hydrolyse oestrone sulphate and DHA-S. In addition the ability of an irreversible steroid sulphatase inhibi- tor, oestrone-3-O-sulphamate [16], to inhibit the hy- drolysis of oestrone sulphate and DHA-S by the expressed enzyme was also investigated. 101