Intrinsic isotope effects suggest that the reaction coordinate symmetry for the cytochrome P-450 catalyzed hydroxylation of octane is isozyme independent
- 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), Vol. 33:4; ISSN 0022-2623
- Country of Publication:
- United States
- Language:
- English
Similar Records
Use of isotope effects in the elucidation of aliphatic oxidation as catalyzed by cytochrome P-450
N-methylcarbazole metabolism by a purified isozyme of rat liver microsomal cytochrome P-450: membrane effects and autocatalytic inactivation
Related Subjects
DEUTERIUM
ISOTOPE EFFECTS
MIXED-FUNCTION OXIDASES
ENZYME ACTIVITY
OCTANE
HYDROXYLATION
CYTOCHROMES
ISOENZYMES
MASS SPECTRA
TRACER TECHNIQUES
ALKANES
ENZYMES
HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDOREDUCTASES
OXYGENASES
PIGMENTS
PROTEINS
SPECTRA
STABLE ISOTOPES
550501* - Metabolism- Tracer Techniques