The peroxidatic function of liver microsomal cytochrome P-450: Comparison of hydrogen peroxide and NADPH-catalysed iV-demethylation reactions

Estabrook, Ronald W.; Martin-Wixtrom, Cheryl; Saeki, Yukikazu; Renneberg, Reinhard; Hildebrandt, Alfred G.; Werringloer, J.

doi:10.3109/00498258409151400

Cited by 45 publications

(16 citation statements)

References 44 publications

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“…Interestingly, the rates of O-dealkylation of 7EFC and 7PRF by the CYP2B4 reconstituted systems dropped to very low levels at a 5000:1 PC/ CYP2B4 ratio, whereas that of benzphetamine only decreased gradually after the ratio exceeded 700:1. One possible explanation for the difference observed with BZP may be the evidence that a high proportion of the total CYP2B4-mediated metabolism of this substrate occurs by the peroxidative pathway which circumvents the need for the reductase and P450 to physically interact (Estabrook et al, 1984).…”

Section: Discussionmentioning

confidence: 99%

Physical Incorporation of NADPH-Cytochrome P450 Reductase and Cytochrome P450 into Phospholipid Vesicles Using Glycocholate and Bio-Beads

Reed¹,

Brignac‐Huber²,

Backes³

2007

Drug Metab Dispos

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ABSTRACT:In a previous study from our laboratory (Drug Metab Dispos 34: 660-666, 2006), we found several limitations with published methods (cholate gel filtration and cholate dialysis) for the incorporation of cytochromes P450 and P450 reductase into phospholipid vesicles. We found that a significant proportion of reductase was not incorporated in the vesicles when the amount of reductase was equal to or greater than that of CYP2B4 in the systems reconstituted with phosphatidylcholine. Furthermore, implementation of these methods compromised the ability of the CYP2B4 to form a ferrous carbon monoxy complex. In the current study, a comparison of results using the detergent-dialysis method with five similar detergents having the "bile salt" ring structure showed that glycocholate results in the greatest incorporation of reductase and the least loss in the ferrous carbon monoxy CYP2B4 complex. The method is further improved by using Bio-Beads SM-2 to remove detergent instead of the lengthy dialysis procedure or size exclusion chromatography that significantly dilutes the protein and lipid concentrations of the preparation. The method is shown to be applicable over a range of lipid/CYP2B4 ratios, and by using assay methods for total lipid, reductase, and CYP2B4, this improved reconstitution method resulted in increased incorporation efficiencies while minimizing the protein degradation inherent with these procedures.

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Section: Discussionmentioning

confidence: 99%

Physical Incorporation of NADPH-Cytochrome P450 Reductase and Cytochrome P450 into Phospholipid Vesicles Using Glycocholate and Bio-Beads

Reed¹,

Brignac‐Huber²,

Backes³

2007

Drug Metab Dispos

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“…A knowledge of the mechanism of reaction of hydrogen peroxide with iron(III) porphyrins is germane to our understanding of the mechanisms of the peroxidase (1) and catalase (2) enzymes and the peroxide shunt reaction of the cytochrome P-450 enzymes (3)(4)(5)(6)(7)(8)(9)(10). Though the reaction of hydrogen peroxide with various iron(III) porphyrins in H20 has received considerable attention, we find that much of the past work (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23) is both incomplete and obscured by the occurrence of metalloporphyrin destruction, aggregation in water, and dimerization in basic media.…”

mentioning

confidence: 99%

The pH dependence of the mechanism of reaction of hydrogen peroxide with a nonaggregating, non-mu-oxo dimer-forming iron (III) porphyrin in water.

Bruice¹,

Zipplies²,

Lee³

1986

Proc. Natl. Acad. Sci. U.S.A.

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The pH dependence of the mechanism of reaction of hydrogen peroxide with a nonaggregating, non-,R-oxo dimer-forming iron(HI) porphyrin in water ( Contributed by Thomas C. Bruice, March 3, 1986 ABSTRACT The reaction of hydrogen peroxide with 5, 10,15,20-tetrakis(2,6-dimethyl-3-sulfonatophenyl)porphinatoiron(Il) hydrate [(P)Fem(H20)] has been investigated in water between pH 1 and pH 12. The water-soluble (P)Fe"'(H20) neither aggregates nor forms a ,.-oxo dimer. The pH dependence and rate-limiting second-order rate constants (k1y) for oxygen transfer from H202 and H02 to the iron(III) porphyrin were determined by trapping of the resultant higher-valent iron-ox~o porphyrin species with 2,2'-azinodi(3-ethylbenzthiazoline)-6-sulfonate (ABTS). Reactions were monitored spectrophometrically by following the'appearance of the radical ABTS-+. From a plot of the logarithm of the determined second-order rate constants for reaction of hydrogen peroxide with iron(EI) porphyrin vs. pH, the composition of the

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“…There is a specific response of peroxide-promoted N-oxygenation reactions to the various inducers of the P-450 system: whereas animal pretreatment with phenobarbital causes stimulation of N-oxide formation from stobadine (50) and N,N-dimethylaniline (60), application of 3-methylcholanthrene strongly attenuates the capacity for arylamine N-oxygenation of hepatic microsomal samples (60). The diverse P-450 isozymes thus are assumed to differ widely with respect to their "peroxygenase" potency (46).…”

Section: Oxygenation Of Secondary Andmentioning

confidence: 99%

“…Apart from this mixed-function type of N-oxygenation, peroxidatic mechanisms (46) appear to play a preponderant role in N-oxidative biotransformation by P-450 enzymes of certain aliphatic and alicyclic tertiary amines. Thus, NADPH-driven microsomal N-oxide formation from pargyline, a monoamine oxidase inhibitor, does not exhibit significant reactivity toward prototypic effectors of P-450, suggesting that this pathway is mainly catalyzed by the FMO (47).…”

Section: Participation Of P-450 In the N-mentioning

confidence: 99%

“…Similarly, pregnenolone-16-a-carbonitrile, which induces other members of the P-450 3A subfamily in animals (34), causes an approximate doubling of the rate of N-oxygenation of N,N-dimethylaniline in rabbit liver microsomes (33). Moreover, where P-450-mediated N-oxygenation reactions appear to proceed via peroxide chemistry (48,50,60), pretreatment of the experimental animals with the various inducers can trigger extensive autoxidative H,O, production in microsomal fractions (85) serving to sustain the "peroxygenase" pathway (46) at the expense of FMO involvement.…”

Section: P-450 Versus Fmo-catalyzed N-oxygenation Of Secondary and Tementioning

confidence: 99%

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Some aspects of the role of cytochrome P‐450 isozymes in the n‐oxidative transformation of secondary and tertiary amine compounds

Hlavica¹,

Lehnerer²

1995

J. Biochem. Toxicol.

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Indirect evidence of the participation of cytochrome P-450 (P-450) in the microsomal N-oxygenation of secondary and tertiary nitrogen functions is presented by studies employing diagnostic modifiers of the hemoprotein system as well as antibodies directed toward the diverse P-450 isoforms and NADPHcytochrome P-450 reductase. Experiments with recombinant hemoproteins or P-450 isozymes directly purified from the tissues of various animal species support the results obtained by the inhibitor assays. Although the intermediacy of aminium radicals is thought to be restrictive to P-450-catalyzed N-oxygenation of secondary and tertiary amine groups bearing accessible hydrogens on the a-carbon, numerous exceptions to this rule are documented. It is proposed that aminium radicals partition between oxygen rebound and a-hydrogen abstraction to yield a finite level of N-oxygenated product in all P-450-mediated amine oxidations, the partition ratio depending on the amine structure and particular P-450 isozyme operative. In some instances, N-oxygenation appears to proceed by peroxidatic mechanisms. The relative contribution of P-450 to the N-oxygenation of secondary and tertiary amines in crude preparations or live animals, where competition with the flavin-containing monooxygenase (FMO) OCcurs, seems to be a function of the relative amounts and catalytic capacities of the two enzyme systems. Both parameters are species and tissue dependent. Accordingly, the extent to which P-450 contributes to total N-oxidative turnover of the amine substrates varies from minor to major.

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The peroxidatic function of liver microsomal cytochrome P-450: Comparison of hydrogen peroxide and NADPH-catalysed iV-demethylation reactions

Cited by 45 publications

References 44 publications

Physical Incorporation of NADPH-Cytochrome P450 Reductase and Cytochrome P450 into Phospholipid Vesicles Using Glycocholate and Bio-Beads

Physical Incorporation of NADPH-Cytochrome P450 Reductase and Cytochrome P450 into Phospholipid Vesicles Using Glycocholate and Bio-Beads

The pH dependence of the mechanism of reaction of hydrogen peroxide with a nonaggregating, non-mu-oxo dimer-forming iron (III) porphyrin in water.

Some aspects of the role of cytochrome P‐450 isozymes in the n‐oxidative transformation of secondary and tertiary amine compounds

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