Sulfotransferase 2A1 forms estradiol-17-sulfate and celecoxib switches the dominant product from estradiol-3-sulfate to estradiol-17-sulfate

Using recombinant sulfotransferases (SULTs) expressed in E. coli, beta-estradiol (E2) sulfonation was examined to determine which SULT enzyme is responsible for producing E2-17-sulfate (E2-17-S). SULTs 1A1*1, 1A1*2, 1A3, 1E1 and 2A1 all sulfated E2 to varying extents. No activity was observed with SULTI1B1. Among the SULTs studied, SULT2A1 produced primarily E2-3-sulfate (E2-3-S), but also some E2-17-S and trace amounts of E2 disulfate. SULT2A1 had a K-m, value of 1.52 mu M for formation of E2-3-S and 2.95 mu M for formation of E2-17-S. SULT2A1 had the highest V-max of 493 pmol/min/mg protein for formation of E2-3-S, which was 8.8- and 47-fold higher than the maximal rates of formation of E2-17-S and E2 disulfate, respectively. SULT2A1 formed E2-3-S more efficiently. However, when celecoxib (0-160 mu M) was included in the incubation with either SULT2A1 or human liver cytosol, sulfonation switched from E2-3-S to E2-17-S in a concentration-dependent manner. The ratio of E2-17-S/E2-3-S went up to 15 with SULT2A1, and was saturated at 1 with human liver cytosol. In both cases, more E2-17-S was formed, with the unreacted E2 remained unchanged, suggesting celecoxib probably bound to a separate effector site to cause a conformational change in SULT2A1, which favored production of E2-17-S. The ability of celecoxib to alter the position of sulfonation of E2 may in part explain its success in the experimental prevention and treatment of breast cancer. (c) 2005 Elsevier Ltd. All rights reserved.