Positional specificity of rabbit CYP4B1 for omega-hydroxylation1 of short-medium chain fatty acids and hydrocarbons.
Rabbit CYP4B1 was incubated with a series of fatty acid and hydrocarbon substrates and metabolites were identified by gas chromatography and gas chromatography/mass spectrometry. C-7 to C-10 n-alkyl fatty acids were preferentially hydroxylated at the terminal carbon (omega/omega-1 = 1.1-7.4) with turnover numbers of 1-11 min-1. The C-7 to C-10 n-alkyl hydrocarbons exhibited turnover numbers of 11-33 min-1 for the corresponding reactions and even higher regioselectivities for hydroxylation at the thermodynamically disfavored site (omega/omega-1 = 1.6-23). These results demonstrate a functional link between CYP4B1 and other CYP4 fatty acid hydroxylases, and show further that CYP4B1's unusual positional specificity is not dictated by the presence of a carboxylate (or polar) anchor on the substrate. This suggests the presence of a dominant hydrocarbon binding site which effectively restricts the access of short-medium chain n-alkyl substrates to the perferryl species in the active site of rabbit CYP4B1.
Department of Medicinal Chemistry, University of Washington, Seattle, Washington, 98195, USA.
M B
MB
Fisher
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YM
Zheng
A E
AE
Rettie
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001665:Binding Sites / Q000502:physiology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry*; D006900:Hydroxylation; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013816:Thermodynamics; D015262:Xenobiotics / Q000378:metabolism
D005227:Fatty Acids; D011994:Recombinant Proteins; D015262:Xenobiotics; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C095029:cytochrome P-450 CYP4B1