Isotopically labeled chlorobenzenes as probes for the mechanism of cytochrome P-450 catalyzed aromatic hydroxylation

Journal Article · Tue Nov 14 04:00:00 EST 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00449a010· OSTI ID:6808260

Korzekwa, K R; Swinney, D C; Trager, W F ^[1]

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1. National Heart, Lung and Blood Institute, Bethesda, MD (USA)

Noncompetitive and competitive intermolecular deuterium isotope effects were measured for the cytochrome P-450 catalyzed hydroxylation of a series of selectively deuterated chlorobenzenes. An isotope effect of 1.27 accompanied the meta hydroxylation of chlorobenzene-2H5 as determined by two totally independent methods (EC-LC and GC-MS assays). All isotope effects associated with the meta hydroxylation of chlorobenzenes-3,5-2H2 and -2,4,6-2H3 were approximately 1.1. In contrast, competitive isotope studies on the ortho and para hydroxylation of chlorobenzenes-4-2H1, -3,5-2H2, and -2,4,6-2H3 resulted in significant inverse isotope effects (approximately 0.95) when deuterium was substituted at the site of oxidation whereas no isotope effect was observed for the oxidation of protio sites. These results eliminate initial epoxide formation and initial electron abstraction (charge transfer) as viable mechanisms for the cytochrome P-450 catalyzed hydroxylation of chlorobenzene. The results, however, can be explained by a mechanism in which an active triplet-like oxygen atom adds to the pi system in a manner analogous to that for olefin oxidation. The resulting tetrahedral intermediate can then rearrange to phenol directly or via epoxide or ketone intermediates.

• OSTI ID: 6808260
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 28:23; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

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560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
AROMATICS
BODY
CELL CONSTITUENTS
CHLORINATED AROMATIC HYDROCARBONS
CHROMATOGRAPHY
DEUTERIUM
DIGESTIVE SYSTEM
ENZYMES
GAS CHROMATOGRAPHY
GLANDS
HALOGENATED AROMATIC HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
LIVER
MAMMALS
MASS SPECTROSCOPY
METABOLISM
MICROSOMES
MIXED-FUNCTION OXIDASES
MOLECULAR STRUCTURE
NUCLEI
ODD-ODD NUCLEI
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANOIDS
ORGANS
OXIDOREDUCTASES
OXYGENASES
RATS
RIBOSOMES
RODENTS
SEPARATION PROCESSES
SPECTROSCOPY
STABLE ISOTOPES
TRACER TECHNIQUES
VERTEBRATES