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Calibration of the channel that determines the ω-Hydroxylation regiospecificity of cytochrome P4504A1: catalytic oxidation of 12-HALODOdecanoic acids

MPG-Autoren
http://pubman.mpdl.mpg.de/cone/persons/resource/persons92561

Cryle,  Max
Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Max Planck Society;

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Zitation

He, X., Cryle, M., De Voss, J. J. O., & de Montellano, P. R. (2005). Calibration of the channel that determines the ω-Hydroxylation regiospecificity of cytochrome P4504A1: catalytic oxidation of 12-HALODOdecanoic acids. The Journal of Biological Chemistry, 280(24), 22697-22705. doi:10.1074/jbc.M502632200.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0019-9BBB-2
Zusammenfassung
The fatty acid ω−hydroxylation regiospecificity of CYP4 enzymes may result from presentation of the terminal carbon to the oxidizing species via a narrow channel that restricts access to the other carbon atoms. To test this hypothesis, the oxidation of 12−iodo−, 12−bromo−, and 12−chlorododecanoic acids by recombinant CYP4A1 has been examined. Although all three 12−halododecanoic acids bind to CYP4A1 with similar dissociation constants, the 12−chloro and 12−bromo fatty acids are oxidized to 12−hydroxydodecanoic acid and 12−oxododecanoic acid, whereas the 12−iodo analogue is very poorly oxidized. Incubations in H2182O show that the 12−hydroxydodecanoic acid oxygen derives from water, whereas that in the aldehyde derives from O2. The alcohol thus arises from oxidation of the halide to an oxohalonium species that is hydrolyzed by water, whereas the aldehyde arises by a conventional carbon hydroxylation−elimination mechanism. No irreversible inactivation of CYP4A1 is observed during 12−halododecanoic acid oxidation. Control experiments show that CYP2E1, which has an ω−1 regiospecificity, primarily oxidizes 12−halododecanoic acids to the ω−aldehyde rather than alcohol product. Incubation of CYP4A1 with 12,12−[2H]2−12−chlorododecanoic acid causes a 2−3−fold increase in halogen versus carbon oxidation. The fact that the order of substrate oxidation (Br > Cl » I) approximates the inverse of the intrinsic oxidizability of the halogen atoms is consistent with presentation of the halide terminus via a channel that accommodates the chloride and bromide but not iodide atoms, which implies an effective channel diameter greater than 3.90 Å but smaller than 4.30 &Aring