Abstract
Minoxidil (MNX) is a potent antihypertensive and hair growth promoter. Vasodilatory and hair follicle effects are due to MNX-sulfate, the active metabolite produced by both thermostable and thermolabile phenol sulfotransferases. Because our initial work indicated that DHEA ST might also catalyze MNX sulfation, we tested and characterized human liver cDNA expressed DHEA ST activity with MNX. Apparent Km values for MNX and 3′ -phosphoadenosine-5′ -phosphosulfate were 3. 9 mM and 0. 13 μ M, respectively. Thermal stability of the cDNA encoded DHEA ST activity with MNX and DHEA as substrates was nearly identical as indicated by a 50% inactivation temperature of 42° C for both. The IC50 values for activity assayed with MNX and DHEA were 1. 4 × 10-4 M and 6. 0 × 105 M, respectively. Activity assayed with MNX and DHEA in the presence of NaCI showed activation of 1. 4-fold at 25 mM NaCI and 2. 5-fold at 200 mM NaCI, respectively. HPLC of the reaction product showed that 99% of the net radioactivity coeluted with authentic MNX-sulfate. Conclusion: DHEA ST, an hydroxysteroid ST, catalyzes the sulfation of MNX and must be considered when determining the contribution of human tissue sulfotransferases to MNX sulfation. (Supported, in part, by the VA Medical Research Service and Creighton University).