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Guengerich FP, Fekry MI. Methylene Oxidation of Alkyl Sulfates by Cytochrome P450 BM-3 and a Role for Conformational Selection in Substrate Recognition. ACS Catal 2020; 10:5008-5022. [PMID: 34327041 DOI: 10.1021/acscatal.0c00677] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cytochrome P450BM-3 (P450BM-3) is a flavoprotein reductase-heme fusion protein from the bacterium Bacillus megaterium that has been well-characterized in many biophysical aspects. Although the enzyme is known to catalyze the hydroxylation of medium and long-chain fatty acids at high rates, no definitive physiological function has been associated with this process in the organism other than a possible protective role. We found that P450BM-3 rapidly hydroxylates alkyl sulfates, particularly those with 12-16 carbons (i.e., including dodecyl sulfate) in a similar manner to the fatty acids. The products were characterized as primarily ω-1 hydroxylated alkyl sulfates (plus some ω-2 and ω-3 hydroxylation products), and some further oxidation to dihydroxy and keto derivatives also occurred. Binding of the alkyl sulfates to P450BM-3 converted the iron from the low-spin to high-spin form in a saturable manner, consistent with the catalytic results. Rates of binding decreased as a function of increasing concentration of dodecyl sulfate or the fatty acid myristate. This pattern is consistent with a binding model involving multiple events and with conformational selection (equilibrium of the unbound enzyme prior to binding) instead of an induced fit mechanism. Neither C-H bond-breaking nor product release was found to be rate-limiting in the oxidation of lauric acid. The conformational selection results rationalize some known crystal structures of P450BM-3 and can help explain the flexibility of P450BM-3 and engineered forms in accepting a great variety of substrates.
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Affiliation(s)
- F. Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, United States
| | - Mostafa I. Fekry
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, United States
- Department of Pharmacognosy, Faculty of Pharmacy, Cairo University, 11562 Cairo, Egypt
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Kim D, Cha GS, Nagy LD, Yun CH, Guengerich FP. Kinetic analysis of lauric acid hydroxylation by human cytochrome P450 4A11. Biochemistry 2014; 53:6161-72. [PMID: 25203493 PMCID: PMC4188250 DOI: 10.1021/bi500710e] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Cytochrome P450 (P450) 4A11 is the
only functionally active subfamily
4A P450 in humans. P450 4A11 catalyzes mainly ω-hydroxylation
of fatty acids in liver and kidney; this process is not a major degradative
pathway, but at least one product, 20-hydroxyeicosatetraenoic acid,
has important signaling properties. We studied catalysis by P450 4A11
and the issue of rate-limiting steps using lauric acid ω-hydroxylation,
a prototypic substrate for this enzyme. Some individual reaction steps
were studied using pre-steady-state kinetic approaches. Substrate
and product binding and release were much faster than overall rates
of catalysis. Reduction of ferric P450 4A11 (to ferrous) was rapid
and not rate-limiting. Deuterium kinetic isotope effect (KIE) experiments
yielded low but reproducible values (1.2–2) for 12-hydroxylation
with 12-2H-substituted lauric acid. However, considerable
“metabolic switching” to 11-hydroxylation was observed
with [12-2H3]lauric acid. Analysis of switching
results [Jones, J. P., et al. (1986) J. Am. Chem. Soc.108, 7074–7078] and the use of tritium KIE
analysis with [12-3H]lauric acid [Northrop, D. B. (1987) Methods Enzymol.87, 607–625] both
indicated a high intrinsic KIE (>10). Cytochrome b5 (b5) stimulated steady-state
lauric acid ω-hydroxylation ∼2-fold; the apoprotein was
ineffective, indicating that electron transfer is involved in the b5 enhancement. The rate of b5 reoxidation was increased in the presence of ferrous
P450 mixed with O2. Collectively, the results indicate
that both the transfer of an electron to the ferrous·O2 complex and C–H bond-breaking limit the rate of P450 4A11
ω-oxidation.
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Affiliation(s)
- Donghak Kim
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
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Mannering GJ. A life in science: biochemist-nutritionist-forensic toxicologist-pharmacologist. Drug Metab Rev 2001; 33:81-116. [PMID: 11270663 DOI: 10.1081/dmr-100000265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- G J Mannering
- Department of Pharmacology, School of Medicine, University of Minnesota, Minneapolis 55455, USA
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4
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Lazard D, Zupko K, Poria Y, Nef P, Lazarovits J, Horn S, Khen M, Lancet D. Odorant signal termination by olfactory UDP glucuronosyl transferase. Nature 1991; 349:790-3. [PMID: 1900353 DOI: 10.1038/349790a0] [Citation(s) in RCA: 187] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The onset of olfactory transduction has been extensively studied, but considerably less is known about the molecular basis of olfactory signal termination. It has been suggested that the highly active cytochrome P450 monooxygenases of olfactory neuroepithelium are termination enzymes, a notion supported by the identification and molecular cloning of olfactory-specific cytochrome P450s (refs. 13-16). But as reactions catalysed by cytochrome P450 (refs 17, 18) often do not significantly alter volatility, lipophilicity or odour properties, cytochrome P450 may not be solely responsible for olfactory signal termination. In liver and other tissues, drug hydroxylation by cytochrome P450 is frequently followed by phase II biotransformation, for example by UDP glucuronosyl transferase (UGT), resulting in a major change of solubility and chemical properties. We report here the molecular cloning and expression of an olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows preference for odorants over standard UGT substrates. Furthermore, glucuronic acid conjugation abolishes the ability of odorants to stimulate olfactory adenylyl cyclase. This, together with the known broad spectrum of drug-detoxification enzymes, supports a role for olfactory UGT in terminating diverse odorant signals.
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Affiliation(s)
- D Lazard
- Department of Membrane Research, Weizmann Institute of Science, Rehovot, Israel
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Karp F, Harris JL, Croteau R. Metabolism of monoterpenes: demonstration of the hydroxylation of (+)-sabinene to (+)-cis-sabinol by an enzyme preparation from sage (Salvia officinalis) leaves. Arch Biochem Biophys 1987; 256:179-93. [PMID: 3111374 DOI: 10.1016/0003-9861(87)90436-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A microsomal preparation from the epidermis of Salvia officinalis leaves catalyzed the NADPH- and O2-dependent hydroxylation of the monoterpene olefin (+)-sabinene to (+)-cis-sabinol. The reaction catalyzed is a key step in the biosynthesis of C3-oxygenated thujane monoterpenes, and the hydroxylase is highly specific for (+)-sabinene as substrate. The hydroxylase from leaf homogenates was solubilized and characterized with regard to reaction conditions, inhibitors, and activators. Activity was partially inhibited by rabbit anti-rat cytochrome P-450 and by CO, and the latter inhibition was reversed by 450 nm light. A CO-difference spectrum and type I substrate binding spectrum were obtained. The hydroxylase meets most of the established criteria for a cytochrome P-450-dependent mixed function oxygenase and represents one of very few enzyme systems of this type to be isolated from leaves of a higher plant.
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Iba MM, Mannering GJ. NADPH- and linoleic acid hydroperoxide-induced lipid peroxidation and destruction of cytochrome P-450 in hepatic microsomes. Biochem Pharmacol 1987; 36:1447-55. [PMID: 3579983 DOI: 10.1016/0006-2952(87)90109-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Temporal aspects of the effects of inhibitors on hepatic cytochrome P-450 destruction and lipid peroxidation induced by NADPH and linoleic acid hydroperoxide (LAHP) were compared. In the absence of added Fe2+, NADPH-induced lipid peroxidation in hepatic microsomes exhibited a slow phase followed by a fast phase. The addition of Fe2+ eliminated the slow phase, thus demonstrating that iron is a rate-limiting component in the reaction. EDTA, which complexes iron, and p-chloromercurobenzoate (pCMB), which inhibits NADPH-cytochrome P-450 reductase, inhibited both phases of the reaction. Catalase as well as scavengers of hydroxyl radical, inhibited NADPH-induced lipid peroxidation almost completely. GSH also inhibited the NADPH-dependent reaction but only when added at the beginning of the reaction. In contrast with NADPH-dependent lipid peroxidation, the autocatalytic reaction induced by LAHP was not biphasic, NADPH-dependent or iron-dependent, nor was it inhibited by hydroxyl radical scavengers, catalase or GSH. A synergistic effect on lipid peroxidation was observed when both NADPH and LAHP were added to microsomes. It is concluded that both the fast and slow phases of NADPH-dependent microsomal lipid peroxidation are catalyzed enzymatically and are dependent upon Fe2+, whereas LAHP-dependent lipid peroxidation is autocatalytic. Since the fast phase of enzymatic lipid peroxidation occurred during the fast phase of destruction of cytochrome P-450, it is postulated that iron made available from cytochrome P-450 is sufficient to promote optimal lipid peroxidation. Since catalase and hydroxyl radical scavengers inhibited NADPH-dependent but not LAHP-dependent lipid peroxidation, it is concluded that the hydroxyl radical derived from H2O2 is the initiating active-oxygen species in the enzymatic reaction but not in the autocatalytic reaction.
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Engelmann GL, Staecker JL, Richardson AG. Effect of sodium butyrate on primary cultures of adult rat hepatocytes. IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY : JOURNAL OF THE TISSUE CULTURE ASSOCIATION 1987; 23:86-92. [PMID: 2880833 DOI: 10.1007/bf02623587] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Sodium butyrate, at millimolar concentrations, seems to mediate or initiate multiple effects on many mammalian cells in culture. Although many transformed cell lines respond to butyrate treatment with acquisition of normal cellular characteristics, the effect of butyrate on a normal cell type, the parenchymal hepatocyte, has not been studied. Serum-free primary cultures of adult rat hepatocytes maintain many adult characteristics, yet after several days in culture a loss of adult characteristics occurs while fetal characteristics are often reexpressed. Therefore, we investigated whether butyrate treatment would improve the morphologic and biochemical characteristics of cultured hepatocytes. Exposure to 5 mM butyrate for 3 d did not affect hepatocyte viability or morphology but retarded the progressive decline in cytochrome P-450 levels and 5'-nucleotidase activity. The spontaneous increase in alkaline phosphatase activity was reduced and the induction of tyrosine aminotransferase was inhibited after 3 d in culture. The fetal liver characteristic, gamma glutamyltranspeptidase, was not affected by butyrate treatment. Results of this study suggest that butyrate represents a nontoxic compound capable of improving the maintenance of cell culture characteristics of adult rat hepatocytes.
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Nazario M. The hepatic and renal mechanisms of drug interactions with cimetidine. DRUG INTELLIGENCE & CLINICAL PHARMACY 1986; 20:342-8. [PMID: 2872043 DOI: 10.1177/106002808602000502] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Cimetidine is one of the most frequently prescribed drugs with a known potential to interfere with the metabolic disposition of numerous other medications. Some of these drug interactions may be hazardous to patients. The hepatic and renal mechanisms of drug interactions with cimetidine are discussed in this article. The interactive processes include inhibition of hepatic microsomal enzyme activity, reduction of liver blood flow, and competition for renal tubular secretory sites. The clinical significance and proposed mechanisms of interaction for individual drugs are also presented.
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10
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Gurumurthy P, Mannering GJ. Membrane bound cytochrome P-450 determines the optimal temperatures of NADPH-cytochrome P-450 reductase and cytochrome P-450-linked monooxygenase reactions in rat and trout hepatic microsomes. Biochem Biophys Res Commun 1985; 127:571-7. [PMID: 3919733 DOI: 10.1016/s0006-291x(85)80198-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The hepatic monooxygenase systems largely responsible for the biotransformation of drugs and other xenobiotics are comprised of NADPH-cytochrome P-450 reductase and multiple forms of cytochrome P-450. Optimal temperatures for these systems in the trout and rat are 26 degrees and 37 degrees, respectively. Purified trout and rat reductases are optimally functional at 26 degrees and 37 degrees, respectively, when added to trout and rat microsomes. However, rat reductase was shown to function optimally at 26 degrees when added to trout microsomes and trout reductase functioned optimally at 37 degrees when added to rat microsomes. Corresponding shifts in optimal temperatures of cytochrome P-450-linked 0-deethylation of 7-ethoxycoumarin occurred when these reductases were added to rat or trout microsomes. It is proposed that the phospholipid annulus surrounding the active site of membrane-bound cytochrome P-450 determines the optimal temperature of cytochrome P-450 systems.
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11
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Williams JF, Szentivanyi A. Pharmacokinetic and Pharmacodynamic Parameters Affected by RE Cell Activators. Pharmacology 1985. [DOI: 10.1007/978-1-4615-9406-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Benzo(a)pyrene activation to 7,8-dihydrodiol 9,10-oxide by rat liver microsomes. Control by selective product inhibition. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(18)89812-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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13
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Smith BA, Gutmann HR. Differential effect of chronic ethanol consumption by the rat on microsomal oxidation of hepatocarcinogens and their activation to mutagens. Biochem Pharmacol 1984; 33:2901-10. [PMID: 6541047 DOI: 10.1016/0006-2952(84)90214-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effect of chronic ethanol consumption by rats on hepatic microsomal activation of the hepatocarcinogens dimethylnitrosamine (DMN) and 2-acetylaminofluorene (2-AAF) was investigated. There was a marked increase in the rate of the oxidative demethylation of DMN and its activation to a mutagen by microsomes following ethanol intake. N- and C-hydroxylation of 2-AAF were measured at substrate concentrations ranging from 2 to 70 microM. The ratio of formation of N-hydroxy-2-acetylaminofluorene to C-hydroxy-2-acetylaminofluorenes increased with decreasing substrate concentration, suggesting enhanced carcinogenic potential of 2-AAF with diminishing levels of carcinogen. Kinetic analysis indicated that N-hydroxylation as well as 7-, 5- and 3-hydroxylation of 2-AAF do not follow Michaelis-Menten kinetics. In contrast to the marked inductive effect of ethanol consumption on the metabolic activation of DMN, only a minimal random effect on the N-hydroxylation of 2-AAF was demonstrable in two separate experiments. Furthermore, N-hydroxylation of 2-AAF by microsomes from control and ethanol-treated rats followed similar kinetics. While ethanol consumption enhanced the mutagenic activation of DMN by hepatic microsomes, no such effect of ethanol consumption on the conversion of 2-AAF to a mutagen was observed. The data indicate that chronic ethanol consumption does not have a general inductive effect on the microsomal activation of hepatocarcinogens.
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14
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Fleck C, Bräunlich H. Methods in testing interrelationships between excretion of drugs via urine and bile. Pharmacol Ther 1984; 25:1-22. [PMID: 6387723 DOI: 10.1016/0163-7258(84)90022-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The liver and kidney are largely responsible for inactivating and eliminating drugs and other chemicals. As the excretory capabilities of the two organs overlap, a damage of one system might be compensated by the other. Because of the specificity of both renal and hepatic elimination mechanisms such an alternative excretion route is not possible generally. Several interferences are possible to characterize the relation between hepatic and renal excretion of drugs and xenobiotics. Firstly, the simultaneous assay of excreted drug amounts in urine and bile can give some information concerning the main transport routes of this drug. Thereafter the total interruption of liver or kidney function elucidates the general possibility of alternative excretion routes. But it is important for clinical practice to distinguish between different localizations of organ damages. Today some experimental possibilities exist to exclude partial functions of both kidney and liver separately. Thus it can be clarified why a compound might be excreted via liver or kidney. Moreover it can be characterized whether or not a compensation for the loss of one main excretion organ is possible or not. Such investigations are of some practical importance. Dosing guidelines for drug therapy must be completed for cases of renal or hepatic failure. Moreover the developmental pattern of both elimination routes has consequences for drug use in paediatrics as well as geriatrics. Beside this point of view such investigations are necessary for the prediction of changes in the toxicity of drugs after renal or hepatic insufficiency.
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15
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Gibson GG, Tamburini PP. Cytochrome P-450 spin state: inorganic biochemistry of haem iron ligation and functional significance. Xenobiotica 1984; 14:27-47. [PMID: 6372266 DOI: 10.3109/00498258409151397] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Haem ligation in cytochrome P-450 has been reviewed and the nature of the fifth and sixth ligands of the haemoprotein in the ferric low-spin, ferric high-spin, ferrous and ferrous-carbon-monoxy states have been discussed. Factors controlling the cytochrome P-450 spin equilibrium have been described, including substrate and functional components of the mixed-function oxidase system. In addition, a thermodynamic model describing the interaction of substrate with ferric cytochrome P-450 has been developed in terms of the micro-equilibrium constants governing substrate binding. The functional significance of the cytochrome P-450 spin state with particular reference to control of the first electron reduction of the haemoprotein has been summarized, and a subsequent validation of the spin-redox coupling model of cytochrome P-450-dependent catalysis has been presented.
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16
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Wedlund PJ, Levy RH. Time-dependent kinetics VII: effect of diurnal oscillations on the time course of carbamazepine autoinduction in the rhesus monkey. J Pharm Sci 1983; 72:905-9. [PMID: 6684682 DOI: 10.1002/jps.2600720816] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Extensive blood sampling and repeated long-term carbamazepine infusions were carried out in four rhesus monkeys to examine the time course of carbamazepine autoinduction in detail and assess the intraanimal variability in the rate constant of induction. Diurnal oscillations in carbamazepine blood levels were observed during all infusions and these prevented a good data fit for the biochemical model previously proposed for describing the decline in drug blood levels during induction by carbamazepine. An attempt at fitting only selected blood samples to the model resulted in variable (and perhaps questionable) induction rate constants, even in the same animal. Previous variability in calculated induction rate constants may be due to the presence of diurnal oscillations superimposed on the autoinduction phenomenon. It is proposed that the simultaneous expression of diurnal oscillations and autoinduction are the result of effects on drug metabolism at two independent levels.
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Holtzman JL, Gander JE, Erickson RR. The effect of NADH and low oxygen pressure on the hepatic microsomal ethylmorphine N-demethylase activity of the male rat. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(20)81903-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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18
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Greinert R, Finch SA, Stier A. Cytochrome P-450 rotamers control mixed-function oxygenation in reconstituted membranes. Rotational diffusion studied by delayed fluorescence depolarization. Xenobiotica 1982; 12:717-26. [PMID: 7168192 DOI: 10.3109/00498258209038946] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
1. Rotational diffusion of purified rabbit-liver microsomal cytochrome P-450 LM2 in reconstituted lipid-vesicle membranes was investigated by measurement of time-dependent polarized emission of delayed fluorescence. 2. Cytochrome P-450 labelled with diiodofluorescein iodoacetamide exhibited strict uniaxial rotation about the normal to the membrane. 3. Benzphetamine retards rotation, while reduction of the cytochrome P-450 substrate-complex accelerates rotation. 4. A model is proposed in which cytochrome P-450 forms disc-shaped rotamers immersed in the bilayer membrane to a depth which is varied by substrate-induced and redox state-dependent conformational changes. The model describes a regulating mechanism of the electron transfer-controlling mixed-function oxygenation.
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