Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The vaccinia virus cDNA expression system was used to produce human cytochrome P450 IA2 in a hepatoma cell line that is devoid of significant basal levels of P450. The expressed enzyme yielded a reduced carbon monoxide-bound difference spectrum with a lambda max of 449 nm. Catalytic activities and mutagen activation ability of the human enzyme were assessed and directly compared with results obtained with the orthologous mouse IA2, which was also expressed using vaccinia virus. Both the human and mouse enzymes were able to catalyze efficiently the p-hydroxylation of aniline. Mouse IA2 also catalyzed ethoxyresorufin O-deethylation, and its activity was sevenfold greater than expressed human IA2. The mouse and human enzymes also activated several promutagens and procarcinogens. Mouse IA2 was five- to sevenfold more active than the human enzyme for activation of the procarcinogens 2-acetylaminofluorene and benzo[a]pyrene-trans-7,8-dihydrodiol and the promutagens Glu-P-2 and Trp-P-1. Comparable activities were observed with 2-aminoanthracene, 2-aminofluorene, and Glu-P-1. These data demonstrate the utility of cDNA expression for examining the activities of human P450s and further suggest potentially important differences in catalytic activities of orthologous P450s found in different species.
Mol Carcinog 1989
PMID:Human cDNA-expressed cytochrome P450 IA2: mutagen activation and substrate specificity. 280 20

Reaction thermodynamics have been calculated for an oxene model for cytochrome P-450 oxidations of four related arylamines: aniline, p-hydroxyaniline, acetanilide, and acetaminophen, by both radical and nonradical mechanisms, using a semiempirical molecular orbital method (modified neglect of differential overlap). The results indicate that for both p-hydroxyaniline and acetaminophen, a recently proposed peroxidase-like mechanism leading directly to p-benzoquinoneimines via radical intermediates is thermodynamically favored over N-hydroxylamine formation by H abstraction or addition rearrangement. These studies also provide a detailed characterization of three candidate species for the toxic reactive intermediate of acetaminophen: 1) p-benzoquinoneimines, 2) the radical intermediate formed by H abstraction from the nitrogen, and 3) the radical intermediate formed by H abstraction from the phenol. Calculated electron and spin densities indicate that the radical formed by H abstraction from the phenol oxygen does not remain localized on the oxygen, but is primarily a semiquinone aryl radical with significant unpaired spin density on the ring carbon atoms, particularly on C-3 and C-5. This result is consistent with the hyperfine splitting pattern observed for a transient radical species in a hydroxyl radical-mediated chemical oxidation of acetaminophen. The radical formed by H abstraction from the nitrogen also delocalizes on the ring carbons, but to a lesser extent and at the 2- and 4-positions. A closed shell mechanism of N oxidation of arylamines appears to lead directly to the hydroxylamines with less likelihood of precursor reactive intermediates. Toxic species could then be formed by loss of H2O from the hydroxylamines.
Mol Pharmacol 1985 Mar
PMID:Metabolic activation and toxicity of acetaminophen and related analogs. A theoretical study. 298 85

Treatment of rats with the cytochrome P-450 suicide substrate, 3,5-diethoxycarbonyl-2,6-dimethyl-4-ethyl-1,4-dihydropyridine (DDEP), produced a 95% inhibition of the in vivo demethylation of either aminopyrine or morphine within 2 hr. One-carbon metabolism of formaldehyde or formate to carbon dioxide was not altered. DDEP also produced a time-dependent decrease in total hepatic microsomal cytochrome P-450 but had no effect on either NADPH-cytochrome c reductase or p-nitrophenol glucuronyl-transferase activities up to 24 hr after administration. A rapid decrease in rat liver microsomal aniline hydroxylation and ethoxyresorufin deethylation was observed in vitro following DDEP administration. Although in vitro testosterone metabolism to 16 alpha-, 16 beta-, and 2 alpha-hydroxy metabolites was depressed profoundly by DDEP in microsomes from untreated and 3-methylcholanthrene-treated animals, 7 alpha-hydroxylation of testosterone was much less affected. Immunochemical quantification of various microsomal cytochrome P-450 protein moieties showed that cytochromes P-450 beta NF-B, P-450UT-A, P-450PCN-E, and P-450PB-C were decreased in hepatic microsomes from DDEP-treated rats. However, the protein moiety of cytochrome P-450UT-H was not diminished and the immunoreactive protein for cytochromes P-450UT-F, P-450PB-B, and P-450ISF-G was only slightly decreased. These results show that DDEP treatment leads to marked decreases in holoprotein and apoproteins of many but not all hepatic microsomal cytochrome P-450 isozymes.
Mol Pharmacol 1986 Jan
PMID:Effect of the suicide substrate 3,5-diethoxycarbonyl-2,6-dimethyl-4-ethyl-1,4-dihydropyridine on the metabolism of xenobiotics and on cytochrome P-450 apoproteins. 308 Jun 74

Treatment of male rats for 3 days with the N-substituted imidazole, clotrimazole, produced up to a 4-fold induction of hepatic microsomal cytochrome P-450. The monooxygenase activities induced varied with the dose administered. At low doses (less than 25 mg/kg), p-nitroanisole demethylase and aniline hydroxylase activities were induced. Only at higher doses were other monooxygenase activities (erythromycin and ethylmorphine demethylases and cytochrome P-450 metabolic-intermediate complex formation from troleandomycin) induced. Microsomal UDP-glucuronosyltransferase activity toward morphine was induced at low doses in a manner similar to that of p-nitroanisole demethylase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of microsomes indicated that low doses of clotrimazole caused the intensification of a 48,000 molecular weight protein band, whereas at high doses, there was a marked intensification of an additional 50,500 molecular weight protein, the same molecular weight band as was intensified in phenobarbital- and dexamethasone-induced microsomes. The observations suggest a phenomenon of "dose-differentiated" isozyme induction for cytochrome P-450.
Mol Pharmacol 1987 Feb
PMID:Clotrimazole induction of cytochrome P-450: dose-differentiated isozyme induction. 310 Sep 41

The effects of biliary obstruction and drainage on the hepatic microsomal mixed function oxidase system were studied in rats. Bile duct obstruction produced a significant reduction in the hepatic cytochrome P-450 dependent mixed function oxidase system. After release of the bile duct obstruction, the reduction in microsomal enzymes was practically reversible; however, the process of recovery was slow and differed with the microsomal enzymes in question. Increases in cytochrome b5 content and NADH-cytochrome b5 reductase activity were slower than increases in cytochrome P-450 content and NADPH-cytochrome c reductase activity. Aniline hydroxylase activity increased more rapidly and corresponded to cytochrome P-450 contents more so than did the aminopyrine demethylase activity. After the release of bile duct obstruction, however, the bile acids which had accumulated in the liver during cholestasis were reduced rapidly, to a normal range. These results suggests that there is a discrepancy between reductions in hepatic bile acids and those in the hepatic microsomal mixed function oxidase system after biliary decompression.
Exp Mol Pathol 1988 Aug
PMID:Effects of bile duct obstruction and decompression on hepatic microsomal mixed function oxidase system in rats. 313 3

Hepatic microsomal cytochrome P-450j has been studied using the male spontaneously diabetic BB rat as a model for insulin-dependent diabetes. This approach avoids any direct hepatotoxic effects from chemical diabetogenic agents. Both diabetic rats maintained on insulin and nondiabetic littermates were used as controls. Levels of cytochrome P-450j were increased approximately 3-fold in the diabetics 4 days after the cessation of insulin therapy. In addition, cytochrome P-450j-catalyzed enzymatic activities, aniline hydroxylation, and N-nitrosodimethylamine N-demethylation were increased by the diabetic state at this same time period. Cytochrome P-450f remained at control levels in all groups of animals. In order to test the hypothesis that ketone bodies are involved in the increase in cytochrome P-450j in the diabetic state, plasma beta-hydroxybutyrate levels were monitored. Hepatic aniline hydroxylation, N-nitrosodimethylamine N-demethylation, and cytochrome P-450j levels in individual animals were found to correlate with plasma beta-hydroxybutyrate levels (r = 0.59-0.71 p less than 0.001). In contrast, no significant correlation between levels of cytochrome P-450j and plasma glucose, insulin, or cholesterol was observed in individual animals (r = 0.07-0.23, p greater than 0.4). We conclude that cytochrome P-450j is induced in the livers of spontaneously diabetic rats, and that this induction may be associated directly or indirectly with elevated plasma ketone levels.
Mol Pharmacol 1988 Feb
PMID:Hepatic cytochrome P-450j induction in the spontaneously diabetic BB rat. 327 33

Seventy-two chemicals were tested for their mutagenic potential in the L5178Y tk+/- mouse lymphoma cell forward mutation assay, using procedures based upon those described by Clive and Spector (Mutat Res 44:269-278, 1975) and Clive et al. (Mutat Res 59:61-108, 1979). Cultures were exposed to the chemicals for 4 hr, then cultured for 2 days before plating in soft agar with or without trifluorothymidine (TFT), 3 micrograms/ml. The chemicals were tested at least twice. Significant responses were obtained with allyl isothiocyanate, p-benzoquinone dioxime, benzyl acetate, 2-biphenylamine HCl, bis(2-chloro-1-methylethyl)ether, cadmium chloride, chlordane, chlorobenzene, chlorobenzilate, 2-chloroethanol, chlorothalonil, cytarabine.HCl, p,p'-DDE, diazinon, 2,6-dichloro-p-phenylenediamine, N,N-diethylthiourea, diglycidylresorcinol ether, 2,4-dimethoxy aniline.HCl, disperse yellow 3, endosulfan, 1,2-epoxyhexadecane, ethyl acrylate, ethyl benzene, ethylene thiourea, F D and C yellow Number 6, furan, heptachlor, isophorone, mercuric chloride, 4,4'-methylenedianiline.2 HCl, methyl viologen, nickel sulfate.6H2O, 4,4'-oxydianiline, pentachloroethane, piperonyl butoxide, propyl gallate, quinoline, rotenone, 2,4,5,6-tetrachloro-4-nitro-anisole, 1,1,1,2-tetrachloroethane, trichlorfon, 2,4,6-trichlorophenol, 2,4,5-trimethoxybenzaldehyde, 1,1,3-trimethyl-2-thiourea, 1-vinyl-3-cyclopetene dioxide, vinyl toluene, and ziram. Apart from 2-biphenylamine.HCl, 2-chloroethanol, disperse yellow 3, ethylene thiourea, FD and C yellow number 6, phenol, and 1,1,2-tetrachloroethane, rat liver S9 mix was not a requirement for these compounds. Chemicals not identified as mutagens were acid red, 11-aminoudecanoic acid, boric acid, 5-chloro-o-toluidine, coumaphos, cyclohexanone, decabromodiphenyl oxide, di(2-ethylhexyl)adipate, ferric chloride, fluometuron, melamine, monuron, phenesterin, phthalimide, reserpine, sodium dodecyl sulfate, 4,4-sulfonyldianiline, tetrachloroethylene, and zearalenone. The assay was incapable of providing a clear indication of whether some chemicals were mutagens; these were benzyl alcohol, 1,4-dichlorobenzene, phenol, succinic acid-2,2-dimethyl hydrazide, and toluene.
Environ Mol Mutagen 1988
PMID:Responses of the L5178Y tk+/tk- mouse lymphoma cell forward mutation assay: III. 72 coded chemicals. 338 42

The effect of ethanol consumption by male CF-1 mice on liver microsomal enzyme activities has been investigated. The total microsomal cytochrome P-450 content was increased by 38%, while cytochrome b5 was decreased by 31%, which are characteristic alterations in liver microsomes following ethanol consumption. Other alterations included a decreased NADPH cytochrome c reductase activity and increased NADPH-supported rates of N-nitrosopyrrolidine and aniline hydroxylation. While ethanol consumption did not alter the total metabolism of nicotine, the rates of N- and C-hydroxylation were differently affected. The 5'-hydroxylation of nicotine was increased by 83%, while the N'-oxidation was decreased by 31%. Changes in the microsomal metabolism of the environmental carcinogen 1-nitropyrene included a slight reduction in the overall metabolism, which can be accounted for by a reduction in the formation of one phenolic metabolite, 1-nitropyren-3-ol.
Mol Toxicol
PMID:Differing effects of chronic ethanol consumption by mice on liver microsomal metabolism of xenobiotics: 1-nitropyrene, nicotine, aniline, and N-nitrosopyrrolidine. 344 56

Changes in cytochrome P-450 isoenzymes were studied in rat liver and in primary cultures of rat hepatocytes after treatment with compounds belonging to various classes of inducers, including phenobarbital (PB), beta-naphthoflavone (BNF), and clofibrate/clofibric acid (CLOF/CLOFA). The enzyme activity toward specific substrates was measured, and the presence of apoprotein of several P-450 isoenzymes was determined semiquantitatively by Western blotting. In untreated cultures the P-450 content and activities of 7-ethoxyresorufin O-deethylation (EROD) and aniline 4-hydroxylation (AH) declined with time at different rates. In cultures treated with BNF, the protein levels of isoenzyme P-450IA1 and P-450IA2 were elevated, as in vivo. This induction was reflected in a markedly increased EROD activity. CLOFA enhanced the AH and EROD activity in primary cultures at the same level as in vivo. The monooxygenase activity pentoxyresorufin O-depentylation (PROD) was stimulated by PB and CLOF in vivo, which correlated with the enhanced protein level of P-450IIB1/2. In contrast, the PROD activity was not induced when cultures were treated with PB or CLOFA, although we could detect apoprotein of P-450IIB1/2 by immunoblotting.
Mol Toxicol
PMID:Induction and activity of several isoenzymes of cytochrome P-450 in primary cultures of rat hepatocytes, in comparison with in vivo data. 350 91

Cytosolic liver acetyl-CoA:arylamine N-acetyltransferase (EC 2.3.1.5) from homozygous rapid acetylator rabbits (strain III/J) was purified to homogeneity as judged by gel filtration sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis and isoelectrofocusing. The isoelectric point was estimated to be 5.2. The molecular weight was determined to be 33,500 by sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis and 33,000 by Sephacryl S-200 gel filtration. The amino acid composition is reported and 16 tryptic peptides were sequenced by Edmann degradation, including a peptide from which a very specific oligonucleotide probe can be synthesized. The enzyme contained neither amino sugars nor cofactors. A broad pH optimum from pH 5.9 to 8.6 was observed. N-Acetyltransferase activity showed a strong dependency on the salt concentration. From the influence of the basicity of the acceptor amine on the maximum velocity, it was concluded that the formation of the covalent acetyl-enzyme intermediate is the rate-limiting step in the N-acetyltransferase-catalyzed acetylation of amines. The covalent intermediate reacts, then, in a fast step with the acceptor amine, when using aniline derivatives with pKa values ranging from 5.65 to 1.74. However, with the weakly basic 4-nitroaniline, the acetyltransfer from the catalytic intermediate to the amine seems to be rate-limiting. A structure-activity study of 30 aniline derivatives that differ in hydrophobicity, position, size, charge, and number of substituents showed that some ortho-substituted derivatives were not acetylated.
Mol Pharmacol 1987 Apr
PMID:Purification, physicochemical, and kinetic properties of liver acetyl-CoA:arylamine N-acetyltransferase from rapid acetylator rabbits. 357 90


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