Hydroxylation of chlorzoxazone as a specific probe for human liver cytochrome P-450IIE1

Journal Article · · Chemical Research in Toxicology; (United States)

DOI:https://doi.org/10.1021/tx00018a012· OSTI ID:5144353

Peter, R; Boecker, R ^[1]; Beaune, P H ^[2]; Iwasaki, Masahiko; Guengerich, F P ^[3]; Yang, Chung S ^[4]

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1. Univ. of Erlangen-Nuernberg (Germany)
2. INSERM U75, Paris (France)
3. Vanderbilt Univ., Nashville, TN (United States)
4. Rutgers, The State Univ. of New Jersey, Piscataway (United States)

Human cytochrome P-450IIE1 has been implicated in the oxidation of a number of substrates, including protoxins and carcinogens. To date, no drugs have been identified that are exclusive substrates for the protein and are applicable for as noninvasive probes of the in vivo function of the enzyme in humans. Chlorzoxazone was found to be oxidized only to 6-hydroxychlorzoxazone in human liver microsomes. Results of steady-state kinetics are consistent with the view that only a single enzyme catalyzes the reaction. The microsomal reaction was strongly inhibited by rabbit anti-P0450IIE1 and, in a competitive manner, by known P-450IIE1 substrates. Rates of chlorzoxazone 6-hydroxylation in different human liver microsomal preparations were well correlated with levels of immunochemically measured P-450IIE1 and rates of (CH{sub 3}){sub 2}NNO oxidation. Chlorzoxazone 6-hydroxylation was also found to be catalyzed by purified human oxidation. Chlorzoxazone 6-hydroxylation was also found to be catalyzed by purified human liver P450IIE1. These results provide strong evidence that P-450IIE is the primary catalyst of chlorzoxazone 6-hydroxylation in human liver. Rates of chlorzoxazone 6-hydroxylation vary considerably among human liver samples, and chlorzoxazone 6-hydroxylation may have potential use as a noninvasive probe in estimating the in vivo expression of human P-450IIE1 and its significance as a risk factor in the toxicity and carcinogenicity of a number of solvents, nitrosamines, and drugs.

• OSTI ID: 5144353
• Journal Information: Chemical Research in Toxicology; (United States), Journal Name: Chemical Research in Toxicology; (United States) Vol. 3:6; ISSN 0893-228X; ISSN CRTOE
• Country of Publication: United States
• Language: English

Related Subjects

550500* -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
AMINES
ANIMALS
ANTIBODIES
ANTIGENS
ANTINEOPLASTIC DRUGS
BIOCHEMICAL REACTION KINETICS
BODY
CATALYTIC EFFECTS
CELL CONSTITUENTS
CHEMICAL PREPARATION
CHROMATOGRAPHY
CYTOCHROMES
DIGESTIVE SYSTEM
DRUGS
ENZYME ACTIVITY
ENZYMES
GLANDS
HETEROCYCLIC COMPOUNDS
HYDROXYLATION
IMMUNOSUPPRESSION
IN VITRO
KINETICS
LIQUID COLUMN CHROMATOGRAPHY
LIVER
MAMMALS
MAN
MASS SPECTRA
METABOLISM
MICROSOMES
MIXED-FUNCTION OXIDASES
MOLECULAR STRUCTURE
MONOCLONAL ANTIBODIES
NITROSAMINES
NITROSO COMPOUNDS
NMR SPECTRA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
OXIDOREDUCTASES
OXYGENASES
PIGMENTS
PRIMATES
PROBES
PROTEINS
RABBITS
RATS
REACTION KINETICS
RIBOSOMES
RODENTS
SEPARATION PROCESSES
SPECTRA
SYNTHESIS
VERTEBRATES