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Vavrová K, Indra R, Pompach P, Heger Z, Hodek P. The impact of individual human cytochrome P450 enzymes on oxidative metabolism of anticancer drug lenvatinib. Biomed Pharmacother 2021; 145:112391. [PMID: 34847475 DOI: 10.1016/j.biopha.2021.112391] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 10/20/2021] [Accepted: 11/02/2021] [Indexed: 11/26/2022] Open
Abstract
Lenvatinib, a small molecule tyrosine kinase inhibitor (TKI), exhibits good inhibitory effect in several types of carcinomas. Specifically, it is the most effective TKI used for treatment of thyroid cancer. To extend pharmacokinetics data on this anticancer agent, we aimed to identify the metabolites of lenvatinib formed during in vitro incubation of lenvatinib with human hepatic microsomes or recombinant cytochromes P450 (CYPs) by using high performance liquid chromatography and mass spectrometry. The role of CYPs in the oxidation of lenvatinib was initially investigated in hepatic microsomes using specific CYP inhibitors. CYP-catalytic activities in each microsomal sample were correlated with the amounts of lenvatinib metabolites formed by these samples. Further, human recombinant CYPs were employed in the metabolic studies. Based on our data, lenvatinib is metabolized to O-desmethyl lenvatinib, N-descyclopropyl lenvatinib and lenvatinib N-oxide. In the presence of cytochrome b5, recombinant CYP3A4 was the most efficient to form these metabolites. In addition, CYP1A1 significantly contributes to the lenvatinib metabolism. It was even more efficient in forming of O-desmethyl lenvatinib than CYP3A4 in the absence of cytochrome b5. The present study indicates that further research focused on drug-drug interactions, in particular on CYP3A4 and CYP1A1 modulators, is needed. This will pave new avenues towards TKIs-mediated personalized therapy.
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Affiliation(s)
- Katarína Vavrová
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 128 00 Prague 2, Czech Republic
| | - Radek Indra
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 128 00 Prague 2, Czech Republic.
| | - Petr Pompach
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 128 00 Prague 2, Czech Republic
| | - Zbyněk Heger
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic; Central European Institute of Technology, Brno University of Technology, Purkynova 656/123, 612 00 Brno, Czech Republic
| | - Petr Hodek
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 128 00 Prague 2, Czech Republic
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Indra R, Vavrová K, Pompach P, Heger Z, Hodek P. Identification of Enzymes Oxidizing the Tyrosine Kinase Inhibitor Cabozantinib: Cabozantinib Is Predominantly Oxidized by CYP3A4 and Its Oxidation Is Stimulated by cyt b 5 Activity. Biomedicines 2020; 8:biomedicines8120547. [PMID: 33260548 PMCID: PMC7759869 DOI: 10.3390/biomedicines8120547] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/13/2020] [Accepted: 11/26/2020] [Indexed: 12/24/2022] Open
Abstract
Herein, the in vitro metabolism of tyrosine kinase inhibitor cabozantinib, the drug used for the treatment of metastatic medullary thyroid cancer and advanced renal cell carcinoma, was studied using hepatic microsomal samples of different human donors, human recombinant cytochromes P450 (CYPs), flavin-containing mono-oxygenases (FMOs) and aldehyde oxidase. After incubation with human microsomes, three metabolites, namely cabozantinib N-oxide, desmethyl cabozantinib and monohydroxy cabozantinib, were detected. Significant correlations were found between CYP3A4 activity and generation of all metabolites. The privileged role of CYP3A4 was further confirmed by examining the effect of CYP inhibitors and by human recombinant enzymes. Only four of all tested human recombinant cytochrome P450 were able to oxidize cabozantinib, and CYP3A4 exhibited the most efficient activity. Importantly, cytochrome b5 (cyt b5) stimulates the CYP3A4-catalyzed formation of cabozantinib metabolites. In addition, cyt b5 also stimulates the activity of CYP3A5, whereas two other enzymes, CYP1A1 and 1B1, were not affected by cyt b5. Since CYP3A4 exhibits high expression in the human liver and was found to be the most efficient enzyme in cabozantinib oxidation, we examined the kinetics of this oxidation. The present study provides substantial insights into the metabolism of cabozantinib and brings novel findings related to cabozantinib pharmacokinetics towards possible utilization in personalized medicine.
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Affiliation(s)
- Radek Indra
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 12800 Prague 2, Czech Republic; (K.V.); (P.P.); (P.H.)
- Correspondence: ; Tel.: +420-221-951-285
| | - Katarína Vavrová
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 12800 Prague 2, Czech Republic; (K.V.); (P.P.); (P.H.)
| | - Petr Pompach
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 12800 Prague 2, Czech Republic; (K.V.); (P.P.); (P.H.)
| | - Zbyněk Heger
- Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, 61300 Brno, Czech Republic;
- Central European Institute of Technology, Brno University of Technology, Purkynova 656/123, 61200 Brno, Czech Republic
| | - Petr Hodek
- Department of Biochemistry, Faculty of Science, Charles University, Albertov 6, 12800 Prague 2, Czech Republic; (K.V.); (P.P.); (P.H.)
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Abstract
![]()
Work on the electronic
structures of metal–oxo complexes
began in Copenhagen over 50 years ago. This work led to the prediction
that tetragonal multiply bonded transition metal–oxos would
not be stable beyond the iron–ruthenium–osmium oxo wall
in the periodic table and that triply bonded metal–oxos could
not be protonated, even in the strongest Brønsted acids. In this
theory, only double bonded metal–oxos could attract protons,
with basicities being a function of the electron donating ability
of ancillary ligands. Such correlations of electronic structure with
reactivity have gained importance in recent years, most notably owing
to the widespread recognition that high-valent iron–oxos are
intermediates in biological reactions critical to life on Earth. In this Account, we focus attention on the oxygenations of inert
organic substrates by cytochromes P450, as these reactions involve
multiply bonded iron–oxos. We emphasize that P450 iron–oxos
are strong oxidants, so strong that they would destroy nearby amino
acids if substrates are not oxygenated rapidly; it is our view that
these high-valent iron–oxos are such dangerous reactive oxygen
species that Nature surely found ways to disable them. Looking more
deeply into this matter, mainly by examining many thousands of structures
in the Protein Data Bank, we have found that P450s and other enzymes
that require oxygen for function have chains of tyrosines and tryptophans
that extend from active-site regions to protein surfaces. Tyrosines
are near the heme active sites in bacterial P450s, whereas tryptophan
is closest in most human enzymes. High-valent iron–oxo survival
times taken from hole hopping maps range from a few nanoseconds to
milliseconds, depending on the distance of the closest Trp or Tyr
residue to the heme. In our proposed mechanism, multistep hole tunneling
(hopping) through Tyr/Trp chains guides the damaging oxidizing hole
to the protein surface, where it can be quenched by soluble protein
or small molecule reductants. As the Earth’s oxygenic atmosphere
is believed to have developed about 2.5 billion years ago, the increase
in occurrence frequency of tyrosine and tryptophan since the last
universal evolutionary ancestor may be in part a consequence of enzyme
protective functions that developed to cope with the environmental
toxin, O2.
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Affiliation(s)
- Harry B. Gray
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
| | - Jay R. Winkler
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
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Yablokov E, Florinskaya A, Medvedev A, Sergeev G, Strushkevich N, Luschik A, Shkel T, Haidukevich I, Gilep A, Usanov S, Ivanov A. Thermodynamics of interactions between mammalian cytochromes P450 and b5. Arch Biochem Biophys 2017; 619:10-15. [DOI: 10.1016/j.abb.2017.02.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 02/20/2017] [Accepted: 02/21/2017] [Indexed: 10/20/2022]
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Burkhardt T, Letzel T, Drewes JE, Grassmann J. Comprehensive assessment of Cytochrome P450 reactions: A multiplex approach using real-time ESI-MS. Biochim Biophys Acta Gen Subj 2015; 1850:2573-81. [PMID: 26409144 DOI: 10.1016/j.bbagen.2015.09.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 09/01/2015] [Accepted: 09/22/2015] [Indexed: 01/14/2023]
Abstract
BACKGROUND The detailed analysis of Cytochrome P450 (CYP) catalyzed reactions is of great interest, since those are of importance for biotechnical applications, drug interaction studies and environmental research. Often cocktail approaches are carried out in order to monitor several CYP activities in a single experiment. Commonly in these approaches product formation is detected and IC50 values are determined. METHODS In the present work, the reactions of two different CYP isoforms were monitored using real-time electrospray ionization mass spectrometry. Multiplex experiments using the highly specific CYP2A6 with its corresponding substrate coumarin as well as the highly promiscuous CYP3A4 with testosterone were conducted. Product formation and substrate depletion were simultaneously monitored and compared to the single CYP experiments. The diffusion-controlled rate of reaction and conversion rates that are used as parameters to assess the enzymatic activity were calculated for all measurements conducted. RESULTS Differences in conversion rates and the theoretical rate of reaction that were observed for single CYP and multiplex experiments, respectively, reveal the complexity of the underlying mechanisms. Findings of this study imply that there might be distinct deviations between product formation and substrate degradation when mixtures are used. CONCLUSIONS Detailed results indicate that for a comprehensive assessment of these enzymatic reactions both product and substrate should be considered. GENERAL SIGNIFICANCE The direct hyphenation of enzymatic reactions to mass spectrometry allows for a comprehensive assessment of enzymatic behavior. Due to the benefits of this technique, the entire system which includes substrate, product and intermediates can be investigated. Thus, besides IC50 values further information regarding the enzymatic behavior offers the opportunity for a more detailed insight.
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Affiliation(s)
- Therese Burkhardt
- Chair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall, 85748 Garching, Germany.
| | - Thomas Letzel
- Chair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall, 85748 Garching, Germany.
| | - Jörg E Drewes
- Chair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall, 85748 Garching, Germany.
| | - Johanna Grassmann
- Chair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall, 85748 Garching, Germany.
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Henderson CJ, McLaughlin LA, Scheer N, Stanley LA, Wolf CR. Cytochrome b5 is a major determinant of human cytochrome P450 CYP2D6 and CYP3A4 activity in vivo. Mol Pharmacol 2015; 87:733-9. [PMID: 25657337 DOI: 10.1124/mol.114.097394] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The cytochrome P450-dependent mono-oxygenase system is responsible for the metabolism and disposition of chemopreventive agents, chemical toxins and carcinogens, and >80% of therapeutic drugs. Cytochrome P450 (P450) activity is regulated transcriptionally and by the rate of electron transfer from P450 reductase. In vitro studies have demonstrated that cytochrome b5 (Cyb5) also modulates P450 function. We recently showed that hepatic deletion of Cyb5 in the mouse (HBN) markedly alters in vivo drug pharmacokinetics; a key outstanding question is whether Cyb5 modulates the activity of the major human P450s in drug disposition in vivo. To address this, we crossed mice humanized for CYP2D6 or CYP3A4 with mice carrying a hepatic Cyb5 deletion. In vitro triazolam 4-hydroxylation (probe reaction for CYP3A4) was reduced by >50% in hepatic microsomes from CYP3A4-HBN mice compared with controls. Similar reductions in debrisoquine 4-hydroxylation and metoprolol α-hydroxylation were observed using CYP2D6-HBN microsomes, indicating a significant role for Cyb5 in the activity of both enzymes. This effect was confirmed by the concentration-dependent restoration of CYP3A4-mediated triazolam turnover and CYP2D6-mediated bufuralol and debrisoquine turnover on addition of Escherichia coli membranes containing recombinant Cyb5. In vivo, the peak plasma concentration and area under the concentration time curve from 0 to 8 hours (AUC0-8 h) of triazolam were increased 4- and 5.7-fold, respectively, in CYP3A4-HBN mice. Similarly, the pharmacokinetics of bufuralol and debrisoquine were significantly altered in CYP2D6-HBN mice, the AUC0-8 h being increased ∼1.5-fold and clearance decreased by 40-60%. These data demonstrate that Cyb5 can be a major determinant of CYP3A4 and CYP2D6 activity in vivo, with a potential impact on the metabolism, efficacy, and side effects of numerous therapeutic drugs.
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Affiliation(s)
- Colin J Henderson
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (C.J.H., L.A.M., C.R.W.), TaconicArtemis, Cologne, Germany (N.S.); and Consultant in Investigative Toxicology, Linlithgow, United Kingdom (L.A.S.)
| | - Lesley A McLaughlin
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (C.J.H., L.A.M., C.R.W.), TaconicArtemis, Cologne, Germany (N.S.); and Consultant in Investigative Toxicology, Linlithgow, United Kingdom (L.A.S.)
| | - Nico Scheer
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (C.J.H., L.A.M., C.R.W.), TaconicArtemis, Cologne, Germany (N.S.); and Consultant in Investigative Toxicology, Linlithgow, United Kingdom (L.A.S.)
| | - Lesley A Stanley
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (C.J.H., L.A.M., C.R.W.), TaconicArtemis, Cologne, Germany (N.S.); and Consultant in Investigative Toxicology, Linlithgow, United Kingdom (L.A.S.)
| | - C Roland Wolf
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom (C.J.H., L.A.M., C.R.W.), TaconicArtemis, Cologne, Germany (N.S.); and Consultant in Investigative Toxicology, Linlithgow, United Kingdom (L.A.S.)
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Tralau T, Luch A. The evolution of our understanding of endo-xenobiotic crosstalk and cytochrome P450 regulation and the therapeutic implications. Expert Opin Drug Metab Toxicol 2013; 9:1541-54. [DOI: 10.1517/17425255.2013.828692] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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8
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Functional characterization of eight human CYP1A2 variants: the role of cytochrome b5. Pharmacogenet Genomics 2013; 23:41-52. [PMID: 23295917 DOI: 10.1097/fpc.0b013e32835c2ddf] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Interindividual variability in cytochrome P450 (CYP)-mediated xenobiotic metabolism is extensive. CYP metabolism requires two electrons, which can be donated by NADPH cytochrome P450 oxidoreductase (CYPOR) and/or cytochrome b5 (b5). Although substantial number of studies have reported on the function and effect of b5 in CYP-mediated catalysis, its mode of action is still not fully understood. OBJECTIVE The aim of this work was to examine the effect of b5 on the activities of eight natural-occurring variants of human CYP1A2, namely, T83M, S212C, S298R, G299S, I314V, I386F, C406Y, and R456H. MATERIALS AND METHODS An approach, as used in our former study was applied, coexpressing these polymorphic CYP1A2 variants separately with CYPOR and b5 in the bacterial cell model BTC-CYP. For each variant, 16 different activity parameters were measured, using eight different substrates. This heterogeneous data set was merged with the one of our former study (i.e. without b5) and a multivariate analysis was carried out. RESULTS This analysis indicated that b5 seems to have the ability to affect CYP1A2 variants to behave more like the wild-type variant. This was especially the case for variant I386F, for which the presence of b5 was crucial to show activity. Variants T83M and C406Y showed considerably different activity-profiles when in the presence of b5. Furthermore, our data seem to implicate CYP1A2 residue G299 in its interaction with CYPOR and/or b5. CONCLUSION Results indicate the ability of b5 to affect CYP1A2 variants to behave more like the wild-type variant, attenuating detrimental effects of structural mutations of these variants, seemingly through extensive allosteric effects.
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Munro AW, Girvan HM, Mason AE, Dunford AJ, McLean KJ. What makes a P450 tick? Trends Biochem Sci 2013; 38:140-50. [DOI: 10.1016/j.tibs.2012.11.006] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Revised: 11/15/2012] [Accepted: 11/21/2012] [Indexed: 12/31/2022]
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Dong MS, Lee SB, Kim HJ. Co-expression of human cytochrome b5 increases expression of cytochrome P450 3A4 in Escherichia coli by stabilizing mRNA. Protein Expr Purif 2013; 89:44-50. [PMID: 23459292 DOI: 10.1016/j.pep.2013.02.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 01/22/2013] [Accepted: 02/06/2013] [Indexed: 01/26/2023]
Abstract
CYP3A4 is the most abundant cytochrome P450 in the human liver. The expression level of CYP3A4 when coexpressed with cytochrome b(5) (cyt b(5)) in Escherichia coli was 20-60% higher than that when it was expressed alone over an extended period (48-72 h). This time-dependent elevation in coexpression with cyt b(5) was a result of an increase in CYP3A4 mRNA half-life; no significant change in CYP3A4 degradation was seen in the bacterial protease fraction. These results suggest that the higher CYP3A4 levels observed upon coexpression with cyt b(5) primarily resulted from CYP3A4 mRNA stabilization by cyt b(5).
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Affiliation(s)
- Mi-Sook Dong
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
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11
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Pandey AV, Flück CE. NADPH P450 oxidoreductase: structure, function, and pathology of diseases. Pharmacol Ther 2013; 138:229-54. [PMID: 23353702 DOI: 10.1016/j.pharmthera.2013.01.010] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Accepted: 12/26/2012] [Indexed: 01/18/2023]
Abstract
Cytochrome P450 oxidoreductase (POR) is an enzyme that is essential for multiple metabolic processes, chiefly among them are reactions catalyzed by cytochrome P450 proteins for metabolism of steroid hormones, drugs and xenobiotics. Mutations in POR cause a complex set of disorders that often resemble defects in steroid metabolizing enzymes 17α-hydroxylase, 21-hydroxylase and aromatase. Since our initial reports of POR mutations in 2004, more than 200 different mutations and polymorphisms in POR gene have been identified. Several missense variations in POR have been tested for their effect on activities of multiple steroid and drug metabolizing P450 proteins. Mutations in POR may have variable effects on different P450 partner proteins depending on the location of the mutation. The POR mutations that disrupt the binding of co-factors have negative impact on all partner proteins, while mutations causing subtle structural changes may lead to altered interaction with specific partner proteins and the overall effect may be different for each partner. This review summarizes the recent discoveries related to mutations and polymorphisms in POR and discusses these mutations in the context of historical developments in the discovery and characterization of POR as an electron transfer protein. The review is focused on the structural, enzymatic and clinical implications of the mutations linked to newly identified disorders in humans, now categorized as POR deficiency.
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Affiliation(s)
- Amit V Pandey
- Department of Pediatrics, Division of Pediatric Endocrinology and Diabetology, University Children's Hospital Bern, and Department of Clinical Research, University of Bern, 3004 Bern, Switzerland.
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Lamba JK, Lin YS, Schuetz EG, Thummel KE. Genetic contribution to variable human CYP3A-mediated metabolism. Adv Drug Deliv Rev 2012. [DOI: 10.1016/j.addr.2012.09.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Fredenhagen A, Kittelmann M, Oberer L, Kuhn A, Kühnöl J, Délémonté T, Aichholz R, Wang P, Atadja P, Shultz MD. Biocatalytic synthesis and structure elucidation of cyclized metabolites of the deacetylase inhibitor panobinostat (LBH589). Drug Metab Dispos 2012; 40:1041-50. [PMID: 22344701 DOI: 10.1124/dmd.111.043620] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Panobinostat (LBH589) is a novel pan-deacetylase inhibitor that is currently being evaluated in phase III clinical trials for treatment of Hodgkin's lymphoma and multiple myeloma. Under catalysis of recombinant human CYP3A4 and CYP2D6 coexpressed with human cytochrome P450 reductase in Escherichia coli JM109, five metabolites of panobinostat were produced via whole-cell biotransformation. The structures of the metabolites were elucidated with the spectroscopic methods mass spectrometry (MS) and NMR and revealed an oxidative cyclization of the ethyl-amino group to the methylindole moiety. The MS(2) spectrum of the cyclized metabolite showed a base peak, where the closed ring is reopened and that, taken as sole base for structure proposals, would have lead to wrong conclusions. The metabolites were substantially less potent deacetylase inhibitors than the parent compound.
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Affiliation(s)
- Andreas Fredenhagen
- Global Ciscovery Chemistry, Novartis Institutes for BioMedical Research, WKL-122.P.37, CH-4002 Basel, Switzerland.
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Erkekoglu P, Giray BK, Caglayan A, Hincal F. Selenium and/or iodine deficiency alters hepatic xenobiotic metabolizing enzyme activities in rats. J Trace Elem Med Biol 2012; 26:36-41. [PMID: 22366236 DOI: 10.1016/j.jtemb.2011.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 10/10/2011] [Accepted: 12/11/2011] [Indexed: 01/12/2023]
Abstract
The objective of this study was to investigate the effects of iodine (I(2)) and/or selenium (Se) deficiency on thyroid hormones and hepatic xenobiotic metabolizing enzyme systems using a triple animal model. Three-week-old male Wistar rats were fed for seven weeks. Se deficiency was introduced by a diet containing <0.005 mg/kg Se, and I(2) deficiency was produced by sodium perchlorate containing drinking water. The levels of plasma thyroid hormones [total T(4) (TT(4)), total T(3) (TT(3))], thyroid stimulating hormone (TSH); total microsomal cytochrome P450 (CYP450) and cytochrome b5 (CYP b5) levels; activities of microsomal NADPH-cytochrome P450 reductase (P450R), microsomal aniline hydroxylase (CYP2E1), microsomal 7-ethoxyresorufin O-deethylase (EROD), microsomal 7-pentoxyresorufin O-depentylase (PROD) and cytosolic glutathione S-transferase (GST) were determined. In I(2) deficiency total CYP450 levels, activities of CYP2E1, EROD and GST decreased, and CYP b5 content increased significantly. In Se-deficient rats, total CYP450 level and CYP2E1 activity increased, and EROD and GST activities and CYP b5 level decreased significantly. In combined I(2) and Se deficiency, except for CYP450 content and CYP2E1 activity, all enzyme activities and CYP b5 content decreased significantly compared to control group. Overall results of this study have suggested that metabolism of xenobiotics as well as endogenous compounds is affected by Se and I(2) status.
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Affiliation(s)
- Pinar Erkekoglu
- Hacettepe University, Faculty of Pharmacy, Department of Toxicology, Ankara 06100, Turkey
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Comparison of microbial hosts and expression systems for mammalian CYP1A1 catalysis. J Ind Microbiol Biotechnol 2011; 39:275-87. [PMID: 21863302 DOI: 10.1007/s10295-011-1026-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 08/04/2011] [Indexed: 10/17/2022]
Abstract
Mammalian cytochrome P450 enzymes are of special interest as biocatalysts for fine chemical and drug metabolite synthesis. In this study, the potential of different recombinant microorganisms expressing rat and human cyp1a1 genes is evaluated for such applications. The maximum specific activity for 7-ethoxyresorufin O-deethylation and gene expression levels were used as parameters to judge biocatalyst performance. Under comparable conditions, E. coli is shown to be superior over the use of S. cerevisiae and P. putida as hosts for biocatalysis. Of all tested E. coli strains, E. coli DH5α and E. coli JM101 harboring rat CYP1A1 showed the highest activities (0.43 and 0.42 U g⁻¹(CDW), respectively). Detection of active CYP1A1 in cell-free E. coli extracts was found to be difficult and only for E. coli DH5α, expression levels could be determined (41 nmol g⁻¹(CDW)). The presented results show that efficient expression of mammalian cyp1a1 genes in recombinant microorganisms is troublesome and host-dependent and that enhancing expression levels is crucial in order to obtain more efficient biocatalysts. Specific activities currently obtained are not sufficient yet for fine chemical production, but are sufficient for preparative-scale drug metabolite synthesis.
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Wynant I, Durieux A, Bohets H, Lavrijsen K, Horvath G, Simon JP. RecombinantEscherichia colicells immobilized in Ca-alginate beads for metabolite production. BIOCATAL BIOTRANSFOR 2009. [DOI: 10.3109/10242420903286141] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Woodland C, Huang TT, Gryz E, Bendayan R, Fawcett JP. Expression, Activity and Regulation of CYP3A in Human and Rodent Brain. Drug Metab Rev 2008; 40:149-68. [DOI: 10.1080/03602530701836712] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Gan L, von Moltke LL, Trepanier LA, Harmatz JS, Greenblatt DJ, Court MH. Role of NADPH-cytochrome P450 reductase and cytochrome-b5/NADH-b5 reductase in variability of CYP3A activity in human liver microsomes. Drug Metab Dispos 2008; 37:90-6. [PMID: 18838505 DOI: 10.1124/dmd.108.023424] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
NADPH-cytochrome P450 reductase (CPR) and cytochrome-b(5) (b(5)) together with NADH-b(5) reductase (b(5)R) play important roles in cytochrome P450 3A-mediated drug metabolism via electron transfer. However, it is not clear whether variability in expression of these accessory proteins contributes to the known interindividual variability in CYP3A activity. CPR and b(5) were measured in human liver microsomes (HLMs) by spectrophotometry and immunoblotting. HLMs from elderly (>or=46 years) male donors (n=11) averaged 27% (P=0.034) and 41% (P=0.011) lower CPR levels than young (<or=45 years) male donors (n=21) for spectrophotometric and immunoblot values, respectively. Similarly, HLMs from elderly male donors averaged 43% (P=0.034) and 47% (P=0.011) lower b(5) levels than young male donors for spectrophotometric and immunoblot values, respectively. alpha-Lipoic acid and 6-propyl-2-thiouracil were evaluated for selectivity of inhibition of CPR and b(5)R activities, respectively, using recombinant enzymes and HLMs, as well as for effects on CYP3A-mediated triazolam hydroxylation in HLMs with either NADH or beta-NADPH. The results indicate that both compounds are relatively nonselective inhibitors of CPR and b(5)R activities. Finally, we used multivariate regression analysis and showed that variability in CPR or b(5) expression between HLMs does not contribute significantly to variability in CYP3A-mediated midazolam hydroxylation. Consequently, while aging is associated with decreased CPR and b(5) expression in human livers, this effect does not contribute to CYP3A variability.
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Affiliation(s)
- Lu Gan
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, USA
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19
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de Virville JD, Cochet F, Tasseva G, Moreau F, Zachowski A. Changes in electron transport pathways in endoplasmic reticulum of rapeseed in response to cold. PLANTA 2008; 228:875-882. [PMID: 18663470 DOI: 10.1007/s00425-008-0793-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Accepted: 07/11/2008] [Indexed: 05/26/2023]
Abstract
We studied changes induced by cold on electron transfer pathways (linked to NADH or NADPH oxidation) in endoplasmic reticulum of rapeseed hypocotyls (Brassica napus L.) from a freezing-sensitive variety (ISL) and freezing-tolerant variety (Tradition). Plantlets were grown at 22 degrees C then submitted to a cold shock of 13 or 35 days at 4 degrees C. We measured the content in NADH, NADPH, NAD and NADP of the hypocotyls and the redox power was estimated by the reduced versus oxidized nucleotide ratio. The contents in cytochromes b (5) and P-450, electron acceptors of NADH and NADPH respectively, were determined by differential spectrophotometry. Finally, activity of both NADH-cytochrome b (5) reductase (E.C.1.6.2.2) and NADPH cytochrome P-450 reductase (E.C.1.6.2.4) was determined by reduction of exogenous cytochrome c. Results show that during cold shock, along with an increase of linolenic acid content, there was a general activation of the NADPH pathway which was observed more quickly in Tradition plantlets than in ISL ones. Due to transfer of electrons that can occur between NADPH reductase and cytochrome b (5), this could favor fatty acid desaturation in Tradition, explaining why linolenic acid accumulation was more pronounced in this variety. Besides, more cytochrome P-450 accumulated in ISL that could compete for electrons needed by the FAD3 desaturase, resulting in a relative slower enrichment in 18:3 fatty acid in these plantlets.
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Affiliation(s)
- Jacques Davy de Virville
- Laboratoire de Physiologie Cellulaire et Moléculaire des Plantes, Université Pierre et Marie Curie, UMR CNRS 7180, case 154, 3 rue Galilée, Ivry-sur-Seine, 94200, Paris, France.
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20
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Finn RD, McLaughlin LA, Ronseaux S, Rosewell I, Houston JB, Henderson CJ, Wolf CR. Defining the in Vivo Role for cytochrome b5 in cytochrome P450 function through the conditional hepatic deletion of microsomal cytochrome b5. J Biol Chem 2008; 283:31385-93. [PMID: 18805792 PMCID: PMC2581580 DOI: 10.1074/jbc.m803496200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
In vitro, cytochrome b5 modulates the rate of
cytochrome P450-dependent mono-oxygenation reactions. However, the role of
this enzyme in determining drug pharmacokinetics in vivo and the
consequential effects on drug absorption distribution, metabolism, excretion,
and toxicity are unclear. In order to resolve this issue, we have carried out
the conditional deletion of microsomal cytochrome b5 in
the liver to create the hepatic microsomal cytochrome b5
null mouse. These mice develop and breed normally and have no overt phenotype.
In vitro studies using a range of substrates for different P450
enzymes showed that in hepatic microsomal cytochrome b5
null NADH-mediated metabolism was essentially abolished for most substrates,
and the NADPH-dependent metabolism of many substrates was reduced by
50–90%. This reduction in metabolism was also reflected in the in
vivo elimination profiles of several drugs, including midazolam,
metoprolol, and tolbutamide. In the case of chlorzoxazone, elimination was
essentially unchanged. For some drugs, the pharmacokinetics were also markedly
altered; for example, when administered orally, the maximum plasma
concentration for midazolam was increased by 2.5-fold, and the clearance
decreased by 3.6-fold in hepatic microsomal cytochrome b5
null mice. These data indicate that microsomal cytochrome
b5 can play a major role in the in vivo
metabolism of certain drugs and chemicals but in a P450- and
substrate-dependent manner.
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Affiliation(s)
- Robert D Finn
- Cancer Research UK Molecular Pharmacology Unit, Biomedical Research Institute, Level 5, Ninewells Hospital and Medical School, Dundee DD1 9SY, United Kingdom
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21
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Purnapatre K, Khattar SK, Saini KS. Cytochrome P450s in the development of target-based anticancer drugs. Cancer Lett 2008; 259:1-15. [DOI: 10.1016/j.canlet.2007.10.024] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 10/16/2007] [Accepted: 10/17/2007] [Indexed: 11/16/2022]
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22
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Cheng J, Wan DF, Gu JR, Gong Y, Yang SL, Hao DC, Yang L. Establishment of a yeast system that stably expresses human cytochrome P450 reductase: Application for the study of drug metabolism of cytochrome P450s in vitro. Protein Expr Purif 2006; 47:467-76. [PMID: 16434211 DOI: 10.1016/j.pep.2005.11.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Revised: 11/20/2005] [Accepted: 11/25/2005] [Indexed: 11/30/2022]
Abstract
Cytochrome P450s (CYPs) hold a balance in studying pharmacokinetics, toxico-kinetics, drug metabolism, and drug-drug interactions, which require association with cytochrome P450 reductase (CPR) to achieve optimal activity. A novel system of Saccharomyces cerevisiae useful for expression studies of mammalian microsomal CYPs was established. Human CPR (hCPR) was co-expressed with human CYP3A4 (hCYP3A4) in this system, and two expression plasmids pTpLC and pYeplac195-3A4 containing the cDNA of hCPR and hCYP3A4 were constructed, respectively. The two plasmids were applied first and controlled by phosphoglycerate kinase (PGK) promoter. S. cerevisiae BWG1-7alpha transformed with the expression plasmids produced the respective proteins in the expected molecular sizes reactive with both anti-hCYP3A4 immunoglobulin (Ig) and anti-hCPR Ig. The activity of hCPR in yeast BWG-CPR was 443.2 nmol reduced cytochrome c/min/mg, which was about three times the CPR activity of the microsome prepared from the parental yeast. The protein amount of hCYP3A4 in BWG-CPR/3A4 was 35.53 pmol/mg, and the 6beta-hydroxylation testosterone formation activity of hCYP3A4 expressed was 7.5 nmol/min/nmol CYP, 30 times higher than the activity of hCYP3A4 expressed in the parental yeast, and almost two times the activity of hCYP3A4 from homologous human liver microsome. Meanwhile, BWG-CPR/3A4 retained 100 generations under nonselective culture conditions, indicating this yeast was a mitotically stable transformant. BWG-CPR was further tested daily by the PCR amplification of hCPR of yeast genome, Western blot analysis, and the activity assay of hCPR of yeast microsome. This special expression host for CYPs was validated to be stable and efficient for the expression of CYPs, applying as an effective selection model for the drug metabolism in vitro.
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Affiliation(s)
- Jie Cheng
- Laboratory of Pharmaceutical Resource Discovery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, No. 457, People's Republic of China
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23
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Fujita KI, Kamataki T. Genetically engineered bacterial cells co-expressing human cytochrome P450 with NADPH-cytochrome P450 reductase: prediction of metabolism and toxicity of drugs in humans. Drug Metab Pharmacokinet 2005; 17:1-22. [PMID: 15618648 DOI: 10.2133/dmpk.17.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Genetically engineered bacterial cells expressing human cytochrome P450 (CYP) have been developed as new tools to predict the metabolism and toxicity of drugs in humans. There are various host cells for the heterologous expression of a form of CYP. Among them, bacterial cells such as Escherichia coli (E. coli) have advantages with regard to ease of use and high yield of protein. CYP protein could be first expressed by the modification of the N-terminal amino acid sequence in E. coli cells in 1991. Since then, many forms of human CYP have been successfully expressed in E. coli cells. Since the E. coli cells do not possess endogeneous electron transport systems to support the full catalytic activity of CYP, E. coli strains co-expressing both human CYP and NADPH-cytochrome P450 reductase (OR) have been established. Each form of CYP expressed in the E. coli cells efficiently catalyzed the oxidation of a representative substrate at an efficient rate, indicating that the OR was sufficiently expressed to support the catalytic activity of CYP. According to the studies performed so far, the modification of the N-terminal amino acid sequence of CYP did not seem to affect the catalytic properties of CYP. The human CYP expressed in the E. coli cells were applicable for studies to determine a metabolic pathway(s) of drugs and to estimate kinetic parameters of drug metabolism by human CYP. Drug-drug interactions caused by inhibition of the metabolism of drugs by human CYP could also be examined by in vitro inhibition studies with CYP expressed in the E. coli cells. Recently, human CYP was co-expressed with the OR in Salmonella typhimurium (S. typhimurium) cells used for mutation assay (Ames test) by applying the technology for the expression of human CYP and the OR in E. coli cells, to evaluate whether chemicals including drugs are metabolically activated by human CYP and show mutagenicity. These strains of bacteria are considered as useful tools to study the metabolism and the toxicity of drugs in humans.
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Affiliation(s)
- Ken-Ichi Fujita
- Laboratory of Drug Metabolism, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
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Duarte MP, Palma BB, Gilep AA, Laires A, Oliveira JS, Usanov SA, Rueff J, Kranendonk M. The stimulatory role of human cytochrome b5 in the bioactivation activities of human CYP1A2, 2A6 and 2E1: a new cell expression system to study cytochrome P450 mediated biotransformation. Mutagenesis 2005; 20:93-100. [PMID: 15728263 DOI: 10.1093/mutage/gei012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cytochrome b(5) (b(5)) is increasingly recognized to be of importance for specific cytochrome P450 (CYP) activities. We developed human b(5)/CYP-competent mutagenicity tester bacteria to study the role of b(5) in the bioactivation activity of human CYP. These new tester bacteria were derived from the previously engineered human CYP-competent Escherichia coli K12 tester strain MTC, containing a bi-plasmid system for the co-expression of a specific CYP form (CYP1A2, 2A6 or 2E1) with human b(5), and human NADPH cytochrome P450 reductase (RED), resulting in the strain BTC-b(5)-1A2, BTC-b(5)-2A6 and BTC-b(5)-2E1, respectively. The relative content of b(5) with CYP and RED in these three BTC-b(5)-CYP strains demonstrated physiologically relevant co-expression levels and typical CYP-specific activities could be determined with their specific chemical probes. These strains were applied in mutagenicity assays along with their corresponding b(5)-void strains to determine the effect of b(5) on the CYP1A2-, CYP2A6- and CYP2E1-mediated bioactivation of several promutagens. For CYP1A2, of the 5 compounds tested [2-aminoanthracene (2AA), 1-aminopyrene, 6-aminochrysene, 2-amino-3-methylimidazo(4,5-f)quinoline and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)], only the mutagenicity of 2AA was slightly increased ( approximately 1.5-fold) in the presence of b(5). The CYP2E1- and CYP2A6-dependent mutagenicity of N-nitrosodiethylamine increased approximately 3- and 23-fold, respectively when the bacteria contained b(5). The CYP2A6-mediated mutagenicity of NNK increased approximately 9-fold when co-expressed with b(5). The stimulatory effect of b(5) on the bioactivation of N-nitrosodi-n-propylamine was most striking. The mutagenicity of this procarcinogen was completely dependent on the co-expression of b(5) with CYP2A6 or CYP2E1. This demonstrates the prominent role of b(5) in the bioactivation of this carcinogen.
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Affiliation(s)
- Maria Paula Duarte
- Department of Genetics, Faculty of Medical Sciences, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal
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25
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Finn RD, Kapelioukh I, Paine MJI. Rainbow tags: a visual tag system for recombinant protein expression and purification. Biotechniques 2005; 38:387-8, 390-2. [PMID: 15789482 DOI: 10.2144/05383st01] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Visualization systems for tracking proteins are standard experimental tools in most areas of biological research apart from protein purification. Here, we have sought to plug this gap by producing red and yellow visual tags using the heme-binding domain of mosquito cytochrome b5 and the flavin mononucleotide (FMN)-binding domain of human P450 reductase. Tests with colorless glutathione-S-transferase (GST) show them to be simple and effective tools for visually identifying correctly folded protein and tracking protein molecules through protein expression and purification. Furthermore, the characteristic absorbance signatures of the colored tags can be used to quantify protein concentrations directly, which allows purification to be linked to colorimetric detection. This technology, which we call Rainbow Tagging, facilitates expression and downstream processing of recombinant proteins, paving the way for the development of automated high-throughput protein expression systems.
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26
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Galetin A, Brown C, Hallifax D, Ito K, Houston JB. UTILITY OF RECOMBINANT ENZYME KINETICS IN PREDICTION OF HUMAN CLEARANCE: IMPACT OF VARIABILITY, CYP3A5, AND CYP2C19 ON CYP3A4 PROBE SUBSTRATES. Drug Metab Dispos 2004; 32:1411-20. [PMID: 15342470 DOI: 10.1124/dmd.104.000844] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A systematic kinetic analysis of the metabolism of five benzodiazepines (low to high clearance compounds) was performed in CYP3A4, CYP3A5, and CYP2C19 baculovirus-expressed recombinant systems. The data obtained in the expression systems were scaled and compared with human liver microsomal predicted clearance and observed in vivo values, using either cytochrome P450 relative activity factors (RAFs) or the relative abundance approach. Interindividual variability, both in content (CYP3A4, CYP3A5) and activity (CYP3A4, CYP3A5, and CYP2C19), were incorporated in the clearance prediction by bootstrap analysis. These resampling Monte Carlo-based simulations were performed to justify any distribution assumptions in the generated range of the predicted clearance due to a limited sample size. This approach allowed extrapolation of the recombinant clearance data to specific population groups and investigation of the role of "minor" forms like CYP3A5 and CYP2C19 in comparison to the most prolific CYP3A4. The use of quinidine 3-hydroxylation and alprazolam 1'-hydroxylation as RAF markers for CYP3A4 and CYP3A5 activity, respectively, and the incorporation of variability improved the clearance prediction of the selected benzodiazepines (apart from flunitrazepam) to within 2-fold of the in vivo value. Clearance estimates from the immunoquantified protein levels were approximately 8-fold lower in comparison to the RAF approach. The differences observed in the benzodiazepine metabolite pathway ratios between CYP3A4 and CYP3A5, particularly for 1'- to 4-hydroxymidazolam and alprazolam, provided a useful measure of interindividual differences within the CYP3A family.
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Affiliation(s)
- Aleksandra Galetin
- School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
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27
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Abstract
Cytochrome b(5), a 17-kDa hemeprotein associated primarily with the endoplasmic reticulum of eukaryotic cells, has long been known to augment some cytochrome P450 monooxygenase reactions, but the mechanism of stimulation has remained controversial. Studies in recent years have clarified this issue by delineating three pathways by which cytochrome b(5) augments P450 reactions: direct electron transfer of both required electrons from NADH-cytochrome b(5) reductase to P450, in a pathway separate and independent of NADPH-cytochrome P450 reductase; transfer of the second electron to oxyferrous P450 from either cytochrome b(5) reductase or cytochrome P450 reductase; and allosteric stimulation of P450 without electron transfer. Evidence now indicates that each of these pathways is likely to operate in vivo.
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Affiliation(s)
- Todd D Porter
- Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536-0082, USA
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28
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Henderson CJ, Otto DME, Carrie D, Magnuson MA, McLaren AW, Rosewell I, Wolf CR. Inactivation of the hepatic cytochrome P450 system by conditional deletion of hepatic cytochrome P450 reductase. J Biol Chem 2003; 278:13480-6. [PMID: 12566435 DOI: 10.1074/jbc.m212087200] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Cytochrome P450 (CYP) monooxygenases catalyze the oxidation of a large number of endogenous compounds and the majority of ingested environmental chemicals, leading to their elimination and often to their metabolic activation to toxic products. This enzyme system therefore provides our primary defense against xenobiotics and is a major determinant in the therapeutic efficacy of pharmacological agents. To evaluate the importance of hepatic P450s in normal homeostasis, drug pharmacology, and chemical toxicity, we have conditionally deleted the essential electron transfer protein, NADH:ferrihemoprotein reductase (EC, cytochrome P450 reductase, CPR) in the liver, resulting in essentially complete ablation of hepatic microsomal P450 activity. Hepatic CPR-null mice could no longer break down cholesterol because of their inability to produce bile acids, and whereas hepatic lipid levels were significantly increased, circulating levels of cholesterol and triglycerides were severely reduced. Loss of hepatic P450 activity resulted in a 5-fold increase in P450 protein, indicating the existence of a negative feedback pathway regulating P450 expression. Profound changes in the in vivo metabolism of pentobarbital and acetaminophen indicated that extrahepatic metabolism does not play a major role in the disposition of these compounds. Hepatic CPR-null mice developed normally and were able to breed, indicating that hepatic microsomal P450-mediated steroid hormone metabolism is not essential for fertility, demonstrating that a major evolutionary role for hepatic P450s is to protect mammals from their environment.
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Affiliation(s)
- Colin J Henderson
- Cancer Research UK Molecular Pharmacology Unit, Biomedical Research Centre, Level 5, Ninewells Hospital & Medical School, Dundee DD1 9SY, United Kingdom
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Lamba JK, Lin YS, Schuetz EG, Thummel KE. Genetic contribution to variable human CYP3A-mediated metabolism. Adv Drug Deliv Rev 2002; 54:1271-94. [PMID: 12406645 DOI: 10.1016/s0169-409x(02)00066-2] [Citation(s) in RCA: 695] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The human CYP3A subfamily plays a dominant role in the metabolic elimination of more drugs than any other biotransformation enzyme. CYP3A enzyme is localized in the liver and small intestine and thus contributes to first-pass and systemic metabolism. CYP3A expression varies as much as 40-fold in liver and small intestine donor tissues. CYP3A-dependent in vivo drug clearance appears to be unimodally distributed which suggests multi-genic or complex gene-environment causes of variability. Interindividual differences in enzyme expression may be due to several factors including: variable homeostatic control mechanisms, disease states that alter homeostasis, up- or down-regulation by environmental stimuli (such as smoking, drug intake, or diet), and genetic mutations. This review summarizes the current understanding and implications of genetic variation in the CYP3A enzymes. Unlike other human P450s (CYP2D6, CYP2C19) there is no evidence of a 'null' allele for CYP3A4. More than 30 SNPs (single nucleotide polymorphisms) have been identified in the CYP3A4 gene. Generally, variants in the coding regions of CYP3A4 occur at allele frequencies <5% and appear as heterozygous with the wild-type allele. These coding variants may contribute to but are not likely to be the major cause of inter-individual differences in CYP3A-dependent clearance, because of the low allele frequencies and limited alterations in enzyme expression or catalytic function. The most common variant, CYP3A4*1B, is an A-392G transition in the 5'-flanking region with an allele frequency ranging from 0% (Chinese and Japanese) to 45% (African-Americans). Studies have not linked CYP3A4*1B with alterations in CYP3A substrate metabolism. In contrast, there are several reports about its association with various disease states including prostate cancer, secondary leukemias, and early puberty. Linkage disequilibrium between CYP3A4*1B and another CYP3A allele (CYP3A5*1) may be the true cause of the clinical phenotype. CYP3A5 is polymorphically expressed in adults with readily detectable expression in about 10-20% in Caucasians, 33% in Japanese and 55% in African-Americans. The primary causal mutation for its polymorphic expression (CYP3A5*3) confers low CYP3A5 protein expression as a result of improper mRNA splicing and reduced translation of a functional protein. The CYP3A5*3 allele frequency varies from approximately 50% in African-Americans to 90% in Caucasians. Functionally, microsomes from a CYP3A5*3/*3 liver contain very low CYP3A5 protein and display on average reduced catalytic activity towards midazolam. Additional intronic or exonic mutations (CYP3A5*5, *6, and *7) may alter splicing and result in premature stop codons or exon deletion. Several CYP3A5 coding variants have been described, but occur at relatively low allelic frequencies and their functional significance has not been established. As CYP3A5 is the primary extrahepatic CYP3A isoform, its polymorphic expression may be implicated in disease risk and the metabolism of endogenous steroids or xenobiotics in these tissues (e.g., lung, kidney, prostate, breast, leukocytes). CYP3A7 is considered to be the major fetal liver CYP3A enzyme. Although hepatic CYP3A7 expression appears to be significantly down-regulated after birth, protein and mRNA have been detected in adults. Recently, increased CYP3A7 mRNA expression has been associated with the replacement of a 60-bp segment of the CYP3A7 promoter with a homologous segment in the CYP3A4 promoter (CYP3A7*1C allele). This mutational swap confers increased gene transcription due to an enhanced interaction between activated PXR:RXRalpha complex and its cognate response element (ER-6). The genetic basis for polymorphic expression of CYP3A5 and CYP3A7 has now been established. Moreover, the substrate specificity and product regioselectivity of these isoforms can differ from that of CYP3A4, such that the impact of CYP3A5 and CYP3A7 polymorphic expression on drug disposition will be drug dependent. In addition to genetic variation, other factors that may also affect CYher factors that may also affect CYP3A expression include: tissue-specific splicing (as reported for prostate CYP3A5), variable control of gene transcription by endogenous molecules (circulating hormones) and exogenous molecules (diet or environment), and genetic variations in proteins that may regulate constitutive and inducible CYP3A expression (nuclear hormone receptors). Thus, the complex regulatory pathways, environmentally susceptible milieu of the CYP3A enzymes, and as yet undetermined genetic haplotypes, may confound evaluation of the effect of individual CYP3A genetic variations on drug disposition, efficacy and safety.
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Andrews J, Abd-Ellah MF, Randolph NL, Kenworthy KE, Carlile DJ, Friedberg T, Houston JB. Comparative study of the metabolism of drug substrates by human cytochrome P450 3A4 expressed in bacterial, yeast and human lymphoblastoid cells. Xenobiotica 2002; 32:937-47. [PMID: 12487724 DOI: 10.1080/00498250210163289] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
1. The aim was to compare the metabolic activity of human CYP3A4 expressed in bacteria (E. coli), yeast (S. cerevisiae) and human lymphoblastoid cells (hBl), with the native CYP3A4 activity observed in a panel of human livers. 2. Three CYP3A4 substrates were selected for study: dextromethorphan (DEM), midazolam (MDZ) and diazepam (DZ). The substrate metabolism in each of the four systems was characterized by deriving the kinetic parameters K(m) or S(50), V(max) and intrinsic clearance (CL(int)) or maximum clearance (CL(max)) from the kinetic profiles; the latter differing by 100-fold across the three substrates. 3. The K(m) or S(50) for the formation of metabolites 3-methoxymorphinan (MEM), 1'-hydroxymidazolam (1'-OH MDZ) and 3-hydroxydiazepam (3HDZ) compared well in all systems. For CYP3A4-mediated metabolism of DEM, MDZ and DZ, the V(max) for hBl microsomes were generally 2-9-fold higher than the respective yeast and human liver microsomes and E. coli membrane preparations, resulting in greater CL(int) or CL(max). In the case of 3HDZ formation, non-linear kinetics were observed for E. coli, hBl microsomes and human liver microsomes, whereas the kinetics observed for S. cerevisiae were linear. 4. The use of native human liver microsomes for drug metabolic studies will always be preferable. However, owing to the limited availability of human tissues, we find it is reasonable to use any of the recombinant systems described herein, since all three recombinant systems gave good predictions of the native human liver enzyme activities.
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Affiliation(s)
- J Andrews
- School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Manchester M13 9PL, UK.
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31
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Hagen N, Olsen AK, Andersen JV, Tjørnelund J, Hansen SH. Characterization of mixtures of recombinant human cytochrome p450s as a screening model for metabolic stability in drug discovery. Xenobiotica 2002; 32:749-59. [PMID: 12396272 DOI: 10.1080/00498250210147124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
1. Recombinant human cytochrome p450 (rhCYP) has become an important screening model in drug metabolism studies due to the high cost of human and animal hepatic tissue. Until now, rhCYPs have been evaluated and used as separate forms, but a mixture of CYP forms comparable with the human liver could be of value in early drug discovery. 2. In the present study, rhCYP2C9, rhCYP2D6 and rhCYP3A4 co-expressed with reductase in Escerichia coli were mixed and evaluated with regards to kinetic properties (K(m) and V(max)). Furthermore, antioxidant was added to investigate whether a free radical scavenger would affect the kinetic parameters. Results were compared with data obtained in human liver microsomes (HLM). 3. Results showed a good correlation between mixed rh CYP data and HLM data for K(m) and V(max). K(m) varied < 3-fold between matrices for CYP2C9 and CYP3A4, whereas the K(m) for CYP2D6 varied up to 4.5-fold. V(max) differed up to 3-fold between matrices for the CYP forms investigated. However, the discrepancy in V(max) may depend on the anticipated level of each form in HLM. The addition of antioxidant increased V(max) for CYP2C9 and CYP2D6 by 75 and 50%, respectively, whereas V(max) for CYP3A4 was unchanged. 4. In conclusion, the rhCYP mixture shows promising results as a predictor of CYP kinetic parameters. Furthermore, addition of antioxidant can in certain cases increase catalytic activity.
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Affiliation(s)
- N Hagen
- Department of Analytical and Pharmaceutical Chemistry, The Royal Danish School of Pharmacy, DK-2100 Copenhagen, Denmark.
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Cooper MT, Porter TD. Cytochrome b(5) coexpression increases the CYP2E1-dependent mutagenicity of dialkylnitrosamines in methyltransferase-deficient strains of Salmonella typhimurium. Mutat Res 2001; 484:61-8. [PMID: 11733072 DOI: 10.1016/s0027-5107(01)00236-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Addition of cytochrome b(5) to recombinant cytochrome P450 2E1 systems has been shown to enhance the metabolism of dialkylnitrosamines in vitro. To determine if this effect could be observed with recombinant expression systems in vivo, we have constructed mutagenicity tester strains that coexpress full-length human cytochrome P450 2E1 (CYP2E1), rat cytochrome P450 reductase, and human cytochrome b(5) in Salmonella typhimurium lacking ogt and ada methyltransferases (YG7104, ogt(-); and YG7108, ogt(-), ada(-)). These new recombinant strains exhibit a four- to five-fold greater mutagenic response to dimethylnitrosamine, diethylnitrosamine, and dipropylnitrosamine than strains that contain only CYP2E1 and reductase, and are over 100-fold more sensitive to nitrosamines than the parental strains in the presence of an exogenous activating system (S9 fraction). The four-fold increase in mutagenicity in the presence of cytochrome b(5) was consistent with increasing alkyl chain length up to dibutylnitrosamine, which was poorly activated by CYP2E1. The greatest enhancement was obtained with a tricistronic construct in which the b(5) cDNA preceded the P450 and reductase cDNAs; placing the b(5) cDNA after the reductase cDNA was substantially less effective. These new, highly sensitive strains may prove useful in the detection of nitrosamine contamination of food and environmental samples.
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Affiliation(s)
- M T Cooper
- Graduate Center for Toxicology, University of Kentucky, Lexington, KY 40536-0305, USA
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Dai D, Bai R, Hodgson E, Rose RL. Cloning, sequencing, heterologous expression, and characterization of murine cytochrome P450 3a25*(Cyp3a25), a testosterone 6beta-hydroxylase. J Biochem Mol Toxicol 2001; 15:90-9. [PMID: 11284050 DOI: 10.1002/jbt.4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A full-length cDNA clone encoding a novel form of the cytochrome P450 3A subfamily (Cyp3a-25) has been isolated from a mouse liver cDNA library. The sequence contained 2010 base pairs and encoded a protein with 503 amino acids. The amino acid sequence shared greater identities with rat CYP3A18 (90%) and golden hamster CYP3A10 (81%) sequences than with known mouse sequences (Cyp3a-11, Cyp3a-13, Cyp3a-16, and Cyp3a-41 [68--70%]). CYP3A25 was expressed in the Escherichia coli PCWori(+) expression vector following slight modifications of the N- and C-terminals of the cDNA. The purified CYP3A25 was recognized on an immunoblot by CYP3A1 antibody and has a molecular weight of 50 kD. CYP3A25 was catalytically active in the 6 beta-hydroxylation of testosterone and the N-demethylation of benzphetamine and erythromycin. It was demonstrated by RT-PCR that the CYP3A25 mRNA is present in both fetal and adult tissues, including liver, lung, intestines, kidney, and brain. Northern blotting demonstrated that expression is greatest in the liver and small intestine.
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Affiliation(s)
- D Dai
- NIEHS, National Institute of Health, Research Triangle Park, NC 27709, USA
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Neff JA, Moody DE. Differential N-demethylation of l-alpha-acetylmethadol (LAAM) and norLAAM by cytochrome P450s 2B6, 2C18, and 3A4. Biochem Biophys Res Commun 2001; 284:751-6. [PMID: 11396966 DOI: 10.1006/bbrc.2001.5054] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Incubation of l-alpha-acetylmethadol (LAAM) or norLAAM with cDNA-expressed P450s 3A4, 2B6, and 2C18 produced significant N-demethylation products. P450s 2C19, 2C8, 3A5, 2C9, 3A7, 1A1, and 2D6 (norLAAM only), also produced detectable product. Coexpression of cytochrome b(5) enhanced LAAM N-demethylation, most dramatically for 3A4, but had marginal effects on norLAAM N-demethylation. Modeling total liver metabolism using immunoquantification and relative activity factors of P450s suggests contributions of P450 3A4 > 2B6 > 2C18, with the importance of 2B6 to 2C isozymes enhanced by relative activity factors. The ratio of dinorLAAM to norLAAM plus dinorLAAM formed from LAAM did not exceed 20%, and was isozyme and cytochrome b(5) coexpression dependent. This ratio decreased with concentration with 3A4, but was relatively constant for 2B6 and 2C18. The human liver microsomes substrate-concentration response was similar to cDNA-expressed 3A4, but the ratio was higher. Changes in the environment of cDNA-expressed 3A4 also effected the magnitude of the ratio, but not the concentration-dependent decrease. These studies show that the N-demethylation of LAAM and norLAAM is not restricted to P450 3A4, particularly P450s 2B6 and 2C18, and suggest that the mechanism of sequential metabolism for 3A4 differs from that of 2B6 and 2C18.
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Affiliation(s)
- J A Neff
- Center for Human Toxicology, University of Utah, Salt Lake City, Utah 84112-9457, USA
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Imaoka S, Hayashi K, Hiroi T, Yabusaki Y, Kamataki T, Funae Y. A transgenic mouse expressing human CYP4B1 in the liver. Biochem Biophys Res Commun 2001; 284:757-62. [PMID: 11396967 DOI: 10.1006/bbrc.2001.5055] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human CYP4B1 protein was expressed in the liver of a transgenic mouse line under the control of the promoter of the human apolipoprotein E (apo E) gene. Hepatic microsomes of transgenic mice catalyzed omega-hydroxylation of lauric acid and also activated 2-aminofluorene (2-AF), which is a typical substrate for CYP4B1, to mutagenic compounds detected by an umu gene expression assay. These activities observed in transgenic mouse were efficiently inhibited by CYP4B1 antibody. However, such inhibition was not observed in control mice. This is the first report to indicate catalytic activities of human CYP4B1. For further characterization of human CYP4B1, a fusion protein of CYP4B1 and NADPH-P450 reductase was expressed in yeast cells. It was able to activate 2-AF and was also able to catalyze omega-hydroxylation of lauric acid. This transgenic mouse line and the recombinant fusion protein provide a useful tool to study human CYP4B1 and its relation to chemical toxicity and carcinogenesis.
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Affiliation(s)
- S Imaoka
- Department of Chemical Biology, Osaka City University Medical School, Asahimachi, Abeno-ku, Osaka, Japan.
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Mulrooney SB, Waskell L. High-level expression in Escherichia coli and purification of the membrane-bound form of cytochrome b(5). Protein Expr Purif 2000; 19:173-8. [PMID: 10833404 DOI: 10.1006/prep.2000.1228] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Expression of the membrane-bound form of rabbit cytochrome b(5) in Escherichia coli has been significantly improved through the use of the T7 expression vector pLW01 (A. Bridges, L. Gruenke, Y.-T. Chang, I. Vakser, G. Loew, and L. Waskell, 1998, J. Biol. Chem. 273, 17036-17049) in conjunction with strain C41(DE3) (B. Miroux and J. Walker, 1996, J. Mol. Biol. 260, 289-298). Cell cultures expressing the cytochrome b(5) contained an average of 820 mg/liter of culture and reached peak levels as high as 1100 mg/liter when higher antibiotic concentrations were used. Maximal levels were obtained from cultures when expression was induced with 10 microM IPTG. Approximately 90% of the cytochrome b(5) was expressed as apoprotein which was reconstituted by addition of exogenous heme. The cytochrome b(5) was purified from detergent-solubilized bacterial membranes using anion-exchange chromatography on DEAE-Sepharose followed by size-exclusion chromatography on Superdex-75. Purification of cytochrome b(5) from a 500-ml culture yielded 121 mg of protein which had a specific content of 50 nmol of heme per milligram of protein with an overall recovery of 35%. The final cytochrome b(5) was free of any detectable contaminants when analyzed by SDS-PAGE.
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Affiliation(s)
- S B Mulrooney
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109-0606, USA
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Kranendonk M, Laires A, Rueff J, Estabrook WR, Vermeulen NP. Heterologous expression of xenobiotic mammalian-metabolizing enzymes in mutagenicity tester bacteria: an update and practical considerations. Crit Rev Toxicol 2000; 30:287-306. [PMID: 10852498 DOI: 10.1080/10408440091159211] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
There is an increasing need for metabolic competent cell systems for the mechanistic studies of biotransformation of xenobiotics in toxicology in general and in genotoxicology in particular. These cell systems combine the heterologous expression of a particular mammalian biotransformation enzyme with a specific target/ end point by which a functional analysis of the expressed gene product in the (geno)toxicity of chemicals can be performed. cDNAs of an increasing number of mammalian biotransformation enzymes is being cloned. The construction of specific expression vectors permits their heterologous expression in laboratory bacteria, such as Escherichia coli strains. This development does not only allow biochemical and enzymatic studies of (pure) enzyme preparations but also facilitates the engineering of metabolically competent mutagenicity tester bacteria, thereby providing new tools for genotoxicity testing and for studying of the roles of biotransformation in chemical carcinogenesis. In this review, we describe an update as well as an evaluation of enzymes expressed in mutagenicity tester bacteria. Four types of biotransformation enzymes are now expressed in these bacteria, namely, GSTs, CYPs, NATs, and STs. The expression of these enzymes in the tester bacteria and their subsequent application in mutagenicity assays demonstrates that heterologous expression in this type of bacteria has a number implications for the functionality of the biotransformation enzymes as well as for the functioning of the tester bacteria in mutagenicity detection. We also describe here a number of practical considerations in this regard.
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Affiliation(s)
- M Kranendonk
- Department of Genetics, Faculty of Medical Sciences, Universidade Nova de Lisboa, Lisbon, Portugal.
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