Abstract
In human adrenarche during childhood, the secretion of dehydroepiandrosterone (DHEA) from the adrenal gland increases due to its increased synthesis and/or decreased metabolism. DHEA is synthesized by 17α-hydroxylase/17,20-lyase, and is metabolized by 3β-hydroxysteroid dehydrogenase type 2 (3βHSD2). In this study, the inhibition of purified human 3βHSD2 by the adrenal steroids, androstenedione, cortisone, and cortisol, was investigated and related to changes in secondary enzyme structure. Solubilized, purified 3βHSD2 was inhibited competitively by androstenedione with high affinity, by cortisone at lower affinity, and by cortisol only at very high, nonphysiologic levels. When purified 3βHSD2 was bound to lipid vesicles, the competitive Ki values for androstenedione and cortisone were slightly decreased, and the Ki value of cortisol was decreased 2.5-fold, although still at a nonphysiologic level. The circular dichroism spectrum that measured 3βHSD2 secondary structure was significantly altered by the binding of cortisol, but not by androstenedione and cortisone. Our import studies show that 3βHSD2 binds in the intermitochondrial space as a membrane-associated protein. Androstenedione inhibits purified 3βHSD2 at physiologic levels, but similar actions for cortisol and cortisone are not supported. In summary, our results have clarified the mechanisms for limiting the metabolism of DHEA during human adrenarche.
Footnotes
- Received August 22, 2014.
- Accepted October 28, 2014.
↵1 Current affiliation: Armstrong Atlantic State University, Savannah, Georgia.
J.A.M. and H.S.B. are cosenior authors and contributed equally to this work.
This work was supported by the National Institutes of Health Eunice Kennedy Shriver National Institute of Child Health and Human Development [Grant HD057876], the Anderson Cancer Institute, and a seed grant from Mercer University (to H.S.B.); by a gift from Boston Children’s Hospital and a Mercer University Seed Grant (to J.L.T.); and by the National Institutes of Health Eunice Kennedy Shriver National Institute of Child Health and Human Development [NIHP30-HD18655] and the Timothy Murphy Fund (to J.A.M.).
- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics
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