title: Cofactors, redox state, and directional preferences of hydroxysteroid dehydrogenases.
abstract: The hydroxysteroid dehydrogenases (HSDs) interconvert pairs of weak and potent steroids, thus serving as key enzymes in the regulation of intracellular hormone potency. These enzymes may appear to drive unidirectional steroid flux in intact cells but actually catalyze bi-directional metabolism that achieve pseudo-equilibria with strong directional preferences. Even small shifts in the magnitude of these pseudo-equilibria can profoundly change steroid potency and thus contribute to disease. Consequently, we are studying the structural and biochemical principles that govern these directional preferences and the resilience of these pseudo-equilibria in intact cells. HSD directional preferences in intact cells are governed largely by relative affinities for nicotinamide cofactors [NAD(P)(H)] and existing cofactor gradients. We can attenuate the directional preferences for human 17betaHSD type 1 and rat AKR1C9 in intact cells by either diminishing the NADPH/NADP(+) gradient or by mutating the arginine residues that form salt bridges with the 2'-phosphate of NADP(H) (R38 and R276, respectively).
authors.affiliation: Division of Endocrinology & Metabolism, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-8857, United States.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Sherbet
authors.forename: Mahboubeh
authors.initials: M
authors.lastname: Papari-Zareei
authors.forename: Naveed
authors.initials: N
authors.lastname: Khan
authors.forename: Kamalesh K
authors.initials: KK
authors.lastname: Sharma
authors.forename: Andrew
authors.initials: A
authors.lastname: Brandmaier
authors.forename: Siayareh
authors.initials: S
authors.lastname: Rambally
authors.forename: Arhana
authors.initials: A
authors.lastname: Chattopadhyay
authors.forename: Stefan
authors.initials: S
authors.lastname: Andersson
authors.forename: Anil K
authors.initials: AK
authors.lastname: Agarwal
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Auchus
mesh_terms: D000818:Animals; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases / Q000737:chemistry / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats
chemical_list: D009249:NADP; D006913:Hydroxysteroid Dehydrogenases