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1 Leiden/Amsterdam Center for Drug Research, Division of Molecular Toxicology, Vrije Universiteit, 1081HV Amsterdam, The Netherlands
2 Institute for Technical Biochemistry, University of Stuttgart, Stuttgart, Germany
(RECEIVED May 8, 2006; FINAL REVISION October 23, 2006; ACCEPTED November 21, 2006)
Hydroxylations of octane and lauric acid by Cytochrome P450-BM3 (CYP102A1) wild-type and three active site mutantsF87A, L188Q/A74G, and F87V/L188Q/A74Gwere rationalized using a combination of substrate orientation from docking, substrate binding statistics from molecular dynamics simulations, and barrier energies for hydrogen atom abstraction from quantum mechanical calculations. Wild-type BM3 typically hydroxylates medium- to long-chain fatty acids on subterminal (
1,
2,
3) but not the terminal (
) positions. The known carboxylic anchoring site Y51/R47 for lauric acid, and hydrophobic interactions and steric exclusion, mainly by F87, for octane as well as lauric acid, play a role in the binding modes of the substrates. Electrostatic interactions between the protein and the substrate strongly modulate the substrate's regiodependent activation barriers. A combination of the binding statistics and the activation barriers of hydrogen-atom abstraction in the substrates is proposed to determine the product formation. Trends observed in experimental product formation for octane and lauric acid by wild-type BM3 and the three active site mutants were qualitatively explained. It is concluded that the combination of substrate binding statistics and hydrogenatom abstraction barrier energies is a valuable tool to rationalize substrate binding and product formation and constitutes an important step toward prediction of product ratios.
Keywords: Cytochrome P450; enzyme catalysis; substrate dynamics; substrate activation barriers; essential dynamics; protein dynamics
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