Intrinsic isotope effects suggest that the reaction coordinate symmetry for the cytochrome P-450 catalyzed hydroxylation of octane is isozyme independent

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · Journal of Medicinal Chemistry; (USA)

DOI:https://doi.org/10.1021/jm00166a024· OSTI ID:7009375

Jones, J P; Rettie, A E; Trager, W F ^[1]

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1. Univ. of Washington, Seattle (USA)

The mechanism of the omega-hydroxylation of octane by three catalytically distinct, purified forms of cytochrome P-450, namely, P-450b, P-450c, and P-450LM2, was investigated by using deuterium isotope effects. The deuterium isotope effects associated with the omega-hydroxylation of octane-1,1,1-2H3, octane-1,8-2H2, and octane-1,1,8,8-2H4 by all three isozymes were determined. From these data the intrinsic isotope effects were calculated and separated into their primary and secondary components. The primary intrinsic isotope effect for the reaction ranged from 7.69 to 9.18 while the secondary intrinsic isotope effect ranged from 1.13 to 1.25. Neither the primary nor secondary isotope effect values were statistically different for any of the isozymes investigated. These data are consistent with a symmetrical transition state for a mechanism involving initial hydrogen atom abstraction followed by hydroxyl radical recombination which is essentially independent of the specific isozyme catalyzing the reaction. It is concluded that (1) in general the porphyrin-(FeO)3+ complex behaves as a source of a triplet-like oxygen atom, (2) the regioselectivity for the site of oxidation is dictated by the apoprotein of the specific isozyme of cytochrome P-450 catalyzing the reaction, and (3) the maximum primary intrinsic isotope effect for any cytochrome P-450 catalyzed oxidation of a carbon center is about 9, assuming no tunneling effects.

• OSTI ID: 7009375
• Journal Information: Journal of Medicinal Chemistry; (USA), Journal Name: Journal of Medicinal Chemistry; (USA) Vol. 33:4; ISSN JMCMA; ISSN 0022-2623
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKANES
CYTOCHROMES
DEUTERIUM
ENZYME ACTIVITY
ENZYMES
HYDROCARBONS
HYDROGEN ISOTOPES
HYDROXYLATION
ISOENZYMES
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
MASS SPECTRA
MIXED-FUNCTION OXIDASES
NUCLEI
OCTANE
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDOREDUCTASES
OXYGENASES
PIGMENTS
PROTEINS
SPECTRA
STABLE ISOTOPES
TRACER TECHNIQUES