Characterization of ethanol-inducible human liver N-nitrosodimethylamine demethylase

Wrighton, Steven; Thomas, Paul E.; Molowa, David T.; Haniu, Mitsuru; Shively, John E.; Maines, Sarah L.; Watkins, Paul B.; Parker, Gary; Méndez-Picón, G; Levin, Wayne

doi:10.1021/bi00370a001

Cited by 169 publications

(67 citation statements)

References 19 publications

(20 reference statements)

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“…29) As listed in Table 1, 4-CBP increased CYP2E1 protein at various doses except for a high dose administration. All of these findings, [22][23][24][25][26][27][28][29] together with our findings ( Table 1), suggest that the increase in CYP2E1 protein by 4-CBP administration can be ascribed to the prevention of CYP 2E1 degradation, and perhaps to mRNA stabilization. However, further detailed study will be needed.…”

Section: Resultssupporting

confidence: 67%

Effect of 4-(4-Chlorobenzyl)pyridine on Rat Hepatic Microsomal Cytochrome P450 and Drug-Metabolizing Enzymes in Vivo and in Vitro.

Kobayashi

Ohshiro

Sasaki

et al. 2001

Biological & Pharmaceutical Bulletin

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The effect of 4-(4-chlorobenzyl)pyridine (4-CBP) on rat hepatic microsomal cytochrome P450 (P450) and its molecular species (CYP2B1, 2E1, 3A2, 2C11, and 2C12), and on drug-metabolizing enzyme activities were examined in vivo and in vitro. Treatment of rats with 4-CBP resulted in the induction of P450 and drug-metabolizing enzymes in a dose-dependent manner, but it was markedly inhibitory at higher dose levels. Immunoblot analyses revealed that 4-CBP induces both CYP2B1 and 2E1; however, both were decreased by increasing the dose of 4-CBP. The in vitro inhibitory experiment revealed that 4-CBP strongly inhibited benzphetamine N-demethylase activity, but not dimethylnitrosamine N-demethylase activity. The present findings provide information on the induction and inhibition effect of chlorinated benzylpyridine on hepatic microsomal P450s and drug-metabolizing enzymes in vivo and in vitro.

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Section: Resultssupporting

confidence: 67%

Effect of 4-(4-Chlorobenzyl)pyridine on Rat Hepatic Microsomal Cytochrome P450 and Drug-Metabolizing Enzymes in Vivo and in Vitro.

Kobayashi

Ohshiro

Sasaki

et al. 2001

Biological & Pharmaceutical Bulletin

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“…Absorbance spectra revealed that the purified CYP2E1 was in a mixed spin state, suggesting that in solution some CYP2E1 protein molecules have water bound to the sixth coordination site of the heme iron, but in other molecules the water is absent, and the heme iron is five-coordinate. Most mammalian P-450s are water-coordinated in the resting state, but this mixed spin state has previously been reported for full-length human CYP2E1, although it has also been isolated as either all high spin or all low spin (37)(38)(39)(40). When reconstituted with NADPH-cytochrome P-450 reductase and cytochrome b 5 , the truncated, purified CYP2E1 is catalytically competent in performing two classic CYP2E1 reactions: 2-hydroxylation of p-nitrophenol and 6-hydroxylation of chlorzoxazone (data not shown).…”

Section: Resultsmentioning

confidence: 76%

“…CYP2C8 has two access channels, one on each side of the BЈ helix (57). The channel in CYP2C9 exits between helices F and I and the C-terminal ␤ 4 sheet system (37). CYP2D6 has the same hydrophilic access channel as CYP2C9 and a second putative channel exiting between the G and I helices (58).…”

Section: Discussionmentioning

confidence: 99%

Structures of Human Cytochrome P-450 2E1

Porubsky¹,

Meneely²,

Scott

2008

Journal of Biological Chemistry

191

102

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Human microsomal cytochrome P-450 2E1 (CYP2E1) monooxygenates >70 low molecular weight xenobiotic compounds, as well as much larger endogenous fatty acid signaling molecules such as arachidonic acid. In the process, CYP2E1 can generate toxic or carcinogenic compounds, as occurs with acetaminophen overdose, nitrosamines in cigarette smoke, and reactive oxygen species from uncoupled catalysis. Thus, the diverse roles that CYP2E1 has in normal physiology, toxicity, and drug metabolism are related to its ability to metabolize diverse classes of ligands, but the structural basis for this was previously unknown. Structures of human CYP2E1 have been solved to 2.2 Å for an indazole complex and 2.6 Å for a 4-methylpyrazole complex. Both inhibitors bind to the heme iron and hydrogen bond to Thr 303 within the active site. Complementing its small molecular weight substrates, the hydrophobic CYP2E1 active site is the smallest yet observed for a human cytochrome P-450. The CYP2E1 active site also has two adjacent voids: one enclosed above the I helix and the other forming a channel to the protein surface. Minor repositioning of the Phe 478 aromatic ring that separates the active site and access channel would allow the carboxylate of fatty acid substrates to interact with conserved 216 QXXNN 220 residues in the access channel while positioning the hydrocarbon terminus in the active site, consistent with experimentally observed -1 hydroxylation of saturated fatty acids. Thus, these structures provide insights into the ability of CYP2E1 to effectively bind and metabolize both small molecule substrates and fatty acids.Cytochrome P-450 (P-450) 3 is a superfamily of enzymes involved in monooxygenation of both endogenous and exogenous substrates. A subset of these enzymes, including cytochrome P-450 2E1 (CYP2E1), are known for their role in the clearance of drugs and other xenobiotics by introducing or unmasking sites for subsequent conjugation and elimination from the body. From a biochemical standpoint these enzymes are fascinating for the diversity of substrates each xenobioticmetabolizing P-450 can metabolize, yet often with exquisite selectivity in the metabolites generated. Unfortunately, in the process some P-450-mediated metabolism can produce toxic or carcinogenic products. Among cytochrome P-450 enzymes, CYP2E1 is particularly notable for this ability and the resulting toxicity (1). This activity is most substantial in the liver because CYP2E1 comprises over 50% of the hepatic cytochrome P-450 mRNA (2) and 7% of the hepatic cytochrome P-450 protein (3). However, CYP2E1 is also expressed at lower levels in a variety of extrahepatic tissues (4), where it is thought to play a role in the metabolism of important endogenous molecules. CYP2E1 levels and the resulting toxicity varies markedly in response to alcohol consumption (5), diabetes (6), obesity (7), and fasting (8). Thus, the action of CYP2E1 can have a significant influence on human health and drug metabolism.CYP2E1 has been connected with liver toxicity through two ...

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“…The inducibility of P450IIIA3 and P450IIE1, in human, has only been recently demonstrated (Watkins et al, 1985;Molowa et al, 1986;Wrighton et al, 1986).…”

Section: Introductionmentioning

confidence: 99%

The increase in urinary excretion of 6 beta‐hydroxycortisol as a marker of human hepatic cytochrome P450IIIA induction.

Ged

Rouillon

Pichard

et al. 1989

Brit J Clinical Pharma

310

156

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1. Urinary excretion of 6 beta‐hydroxycortisol, hepatic microsomal cortisol 6 beta‐hydroxylase and the specific content of several forms of cytochrome P450 were measured in 8 to 14 patients before and after treatment with rifampicin (600 mg orally per day for 4 days). 2. Rifampicin treatment produced an average five fold increase in daily excretion of urinary 6 beta‐hydroxycortisol. 3. Cortisol 6 beta‐ hydroxylase activity increased from 15 +/‐ 6 pmol min‐1 mg‐1 in organ donors (considered as 'control subjects') to 87 +/‐ 31 pmol min‐1 mg‐1 in rifampicin treated patients. 4. Among three forms of human P450 (P450IA, IIC and IIIA), (1), (2), measured by Western blots, only P450IIIA was significantly induced by the antibiotic. 5. Only antibodies against P450IIIA selectively inhibited cortisol 6 beta‐ hydroxylase in human liver microsomes. 6. Cortisol 6 beta‐hydroxylase was correlated with P450IIIA specific content. 7. The urinary level of 6 beta‐hydroxycortisol correlated with liver microsomal cortisol 6 beta‐ hydroxylase and P450IIIA specific content. 8. We conclude that P450IIIA is predominantly responsible for cortisol 6 beta‐hydroxylase activity in human liver microsomes and that urinary 6 beta‐hydroxycortisol is a marker of the induction of this cytochrome P450.

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Characterization of ethanol-inducible human liver N-nitrosodimethylamine demethylase

Cited by 169 publications

References 19 publications

Effect of 4-(4-Chlorobenzyl)pyridine on Rat Hepatic Microsomal Cytochrome P450 and Drug-Metabolizing Enzymes in Vivo and in Vitro.

Effect of 4-(4-Chlorobenzyl)pyridine on Rat Hepatic Microsomal Cytochrome P450 and Drug-Metabolizing Enzymes in Vivo and in Vitro.

Structures of Human Cytochrome P-450 2E1

The increase in urinary excretion of 6 beta‐hydroxycortisol as a marker of human hepatic cytochrome P450IIIA induction.

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