Mechanism-based inactivation of cytochromes P450 2E1 and 2B1 by 5-phenyl-1-pentyne.

doi:10.1006/ABBI.1998.0679

Paper

Mechanism-based inactivation of cytochromes P450 2E1 and 2B1 by 5-phenyl-1-pentyne.

Published Jun 15, 1998 · E. S. Roberts, W. Alworth, P. Hollenberg

Archives of biochemistry and biophysics

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Abstract

A series of acetylenic compounds whose structures were based on "P450 2E1-like" substrates was investigated for their ability to cause inactivation of P450 2E1-dependent p-nitrophenol hydroxylation. The most effective compound with liver microsomes from pyridine-treated rats or with rabbit P450 2E1 in a reconstituted system was 5-phenyl-1-pentyne. The inactivation of purified 2B1, 2E1, a truncated 2E1 lacking amino acids 3-29, 2E1(Delta3-29), or a truncated 2E1 in which threonine 303 was replaced with alanine, 2E1(Delta3-29, T303A), in a reconstituted system by 5-phenyl-1-pentyne was NADPH- and time-dependent and followed pseudo-first-order kinetics. The maximal rate constants for inactivation, the concentrations that gave half-maximal inactivation (KI), and the partition ratios (the number of 5-phenylvaleric acid molecules formed/inactivation event) were determined with each P450. The KI values for 2B1 and 2E1(Delta3-29, T303A) were twice those for 2E1 and 2E1(Delta3-29), and the partition ratios for 2B1 and 2E1(Delta3-29, T303A) were 5-10 times greater than those of 2E1 or 2E1(Delta3-29). During the incubation of P450 2E1 with 5-phenyl-1-pentyne, the loss of P450 as determined by the reduced-CO difference spectra was equal to the loss of catalytic activity. The formation of a heme adduct was demonstrated by HPLC analysis of reaction mixtures containing 5-[3H]phenyl-1-pentyne. HPLC analysis with diode-array detection showed that the Soret region of the proposed heme adduct was different from that of the unmodified heme. The HPLC peak containing the proposed heme adduct was further analyzed by matrix-assisted laser desorption ionization mass spectrometry, and the resulting peaks could result from the addition of a 2-oxo-5-phenylpentyl group to the heme.

In Vitro Study

Study Snapshot

5-phenyl-1-pentyne effectively inactivates cytochromes P450 2E1 and 2B1-dependent p-nitrophenol hydroxylation, leading to the formation of a 2-oxo-5-phenylpentyl group on the heme.

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

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Paper

Mechanism-based inactivation of cytochromes P450 2E1 and 2B1 by 5-phenyl-1-pentyne.

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References

Role of the alanine at position 363 of cytochrome P450 2B2 in influencing the NADPH- and hydroperoxide-supported activities.

The Ala-363 --> Val mutant of cytochrome P450 2B2 exhibits greater NADPH- and hydroperoxide-supported activities than its wild-type counterpart, suggesting its potential importance in metabolizing DMBA.

Inactivation of cytochrome P450s 2B1, 2B4, 2B6, and 2B11 by arylalkynes.

9EPh is the most effective inactivator of cytochrome P450s 2B1, 2B4, 2B6, and 2B11, with its size and shape playing a crucial role in inactivation.

A role for threonine 302 in the mechanism-based inactivation of P450 2B4 by 2-ethynylnaphthalene.

Threonine 302 plays a crucial role in the inactivation of P450 2B4 by 2-ethynylnaphthalene and its covalent modification with 2-naphthylacetic acid.

P450 superfamily: update on new sequences, gene mapping, accession numbers and nomenclature.

This update provides a list of 481 P450 genes and pseudogenes, with 14 families in mammals, and a new nomenclature system for gene identification.

The determination of cytochrome P450 2E1-dependent p-nitrophenol hydroxylation by high-performance liquid chromatography with electrochemical detection.

This sensitive assay using high-performance liquid chromatography with electrochemical detection allows for the determination of 4-nitrocatechol formed during cytochrome P450 2E1-dependent p-nitrophenol hydroxylation, with a linear response based on protein content.

Citations

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Time-dependent enzyme inactivation: Numerical analyses of in vitro data and prediction of drug-drug interactions.

Numerical approaches using ordinary differential equations can improve the parameterization of CYP in vitro kinetics, potentially improving the prediction of clinical drug-drug interactions.

Acetylenes: cytochrome P450 oxidation and mechanism-based enzyme inactivation

Cytochrome P450 oxidation of acetylenes leads to ketene metabolites and enzyme inactivation, with some intermediates forming a ketocarbene-iron heme complex.

Effects of Acetaminophen on Oxidant and Irritant Respiratory Tract Responses to Environmental Tobacco Smoke in Female Mice

Acetaminophen can induce oxidative stress in the respiratory tract and potentiate some responses to environmental tobacco smoke exposure in female mice.

Meclizine, a pregnane X receptor agonist, is a direct inhibitor and mechanism-based inactivator of human cytochrome P450 3A.

Meclizine inhibits human CYP3A enzymes both directly and through mechanism-based inactivation, while norchlorcyclizine is a direct inhibitor but not a mechanism-based inactivator.