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J. Biol. Chem., Vol. 281, Issue 41, 30645-30649, October 13, 2006

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Transition State of the Sulfuryl Transfer Reaction of Estrogen Sulfotransferase^*

Richard H. Hoff, Przemyslaw G. Czyryca, Meihao Sun^¶, Thomas S. Leyh^¶1, and Alvan C. Hengge²

From the Department of Chemistry and Life Science, United States Military Academy, West Point, New York 10996, the Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, and the ^¶Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461

Kinetic isotope effects have been measured for the estrogen sulfotransferase-catalyzed sulfuryl (SO₃) transfer from p-nitrophenyl sulfate to the 5'-phosphoryl group of 3'-phosphoadenosine 5'-phosphate. ¹⁸(V/K)_nonbridge = 1.0016 ± 0.0005, ¹⁸(V/K)_bridge = 1.0280 ± 0.0006, and ¹⁵(V/K) = 1.0014 ± 0.0004. (¹⁵(V/K) refers to the nitro group in p-nitrophenyl sulfate). The kinetic isotope effects indicate substantial SO bond fission in the transition state, with partial charge neutralization of the leaving group. The small kinetic isotope effect in the nonbridging sulfuryl oxygen atoms suggests no significant change in bond orders of these atoms occurs, consistent with modest nucleophilic involvement. A comparison of the data for enzymatic and uncatalyzed sulfuryl transfer reactions suggests that both proceed through very similar transition states.

Received for publication, May 2, 2006 , and in revised form, July 14, 2006.

^* This work was supported by National Institutes of Health Grants GM47297 (to A. C. H.) and GM056248 and GM054469 (to T. S. L.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence may be addressed: Dept. of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461. Tel.: 718-430-2857; Fax: 718-430-8565; E-mail: leyh{at}aecom.yu.edu. ² To whom correspondence may be addressed: Dept. of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300. Tel.: 435-797-3443; Fax: 435-797-3390; E-mail: hengge{at}cc.usu.edu.

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