Structure of human epoxide hydrolase reveals mechanistic inferences on bifunctional catalysis in epoxide and phosphate ester hydrolysis.
The X-ray crystal structure of human soluble epoxide hydrolase (sEH) has been determined at 2.6 A resolution, revealing a domain-swapped quaternary structure identical to that observed for the murine enzyme [Argiriadi, M. A., Morisseau, C., Hammock, B. D., and Christianson, D. W. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 10637-10642]. As with the murine enzyme, the epoxide hydrolytic mechanism of the human enzyme proceeds through an alkyl-enzyme intermediate with Asp-333 in the C-terminal domain. The structure of the human sEH complex with N-cyclohexyl-N'-(iodophenyl)urea (CIU) has been determined at 2.35 A resolution. Tyr-381 and Tyr-465 donate hydrogen bonds to the alkylurea carbonyl group of CIU, consistent with the proposed roles of these residues as proton donors in the first step of catalysis. The N-terminal domain of mammalian sEH contains a 15 A deep cleft, but its biological function is unclear. Recent experiments demonstrate that the N-terminal domain of human sEH catalyzes the metal-dependent hydrolysis of phosphate esters [Cronin, A., Mowbray, S., Dürk, H., Homburg, S., Fleming, I., Fisslthaler, B., Oesch, F., and Arand, M. (2003) Proc. Natl. Acad. Sci. U.S.A. 100, 1552-1557; Newman, J. W., Morisseau, C., Harris, T. R., and Hammock, B. D. (2003) Proc. Natl. Acad. Sci. U.S.A. 100, 1558-1563]. The binding of Mg(2+)-HPO4(2-) to the N-terminal domain of human sEH in its CIU complex reveals structural features relevant to those of the enzyme-substrate complex in the phosphatase reaction.
Gomez
German A
GA
Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
Morisseau
Christophe
C
Hammock
Bruce D
BD
Christianson
David W
DW
D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry; D004851:Epoxide Hydrolases / Q000037:antagonists & inhibitors / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry; D004952:Esters; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000737:chemistry*; D063065:Organophosphonates / Q000737:chemistry*; D010671:Phenylurea Compounds / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000737:chemistry; D012995:Solubility; D013229:Stearic Acids / Q000737:chemistry; D013379:Substrate Specificity
D004791:Enzyme Inhibitors; D004852:Epoxy Compounds; D004952:Esters; D009097:Multienzyme Complexes; D063065:Organophosphonates; D010671:Phenylurea Compounds; D013229:Stearic Acids; C031183:stearic acid; D010744:Phosphoric Monoester Hydrolases; D004851:Epoxide Hydrolases