Expression and characterization of the human 3β-hydroxysteroid sulfotransferases (SULT2B1a and SULT2B1b)

Abstract

The human hydroxysteroid sulfotransferase, dehydroepiandrosterone sulfotransferase (DHEA-ST), is highly expressed in liver and adrenal cortex and displays reactivity towards a broad range of hydroxysteroids including 3β-hydroxysteroids, 3α-hydroxysteroids, estrogens with a 3-phenolic moiety, and 17-hydroxyl group of androgens. In contrast, characterization of the newly described human hydroxysteroid sulfotransferase SULT2B1 isoforms shows that these enzymes are selective for the sulfation of 3β-hydroxysteroids, such as pregnenolone, epiandrosterone, DHEA, and androstenediol. There was no activity detected towards testosterone, dexamethasone, β-estradiol, androsterone, or p-nitrophenol. The SULT2B1 gene encodes two isoforms, SULT2B1a and SULT2B1b, which are generated by alternate splicing of the first exon; therefore the SULT2B1 isoforms differ at their N-terminals. Northern Blot analysis detected a SULT2B1 message in RNA isolated from the human prostate and placenta. No SULT2B1 message was observed in RNA isolated from human liver, colon, lung, kidney, brain, or testis tissue. Purified SULT2B1a was used to generate a specific rabbit polyclonal anti-SULT2B1 antibody. The anti-SULT2B1 antibody did not react with expressed human EST, P-PST-1, M-PST, DHEA-ST, or ST1B2, during immunoblot analysis. The substrate specificity of the expressed SULT2B1 isoforms suggests that these enzymes are capable of regulating the activity of adrenal androgens in human tissues via their inactivation by sulfation.