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Lee GH, Kim V, Lee SG, Jeong E, Kim C, Lee YB, Kim D. Catalytic enhancements in cytochrome P450 2C19 by cytochrome b5. Toxicol Res 2024; 40:215-222. [PMID: 38525137 PMCID: PMC10959859 DOI: 10.1007/s43188-023-00219-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/31/2023] [Accepted: 11/23/2023] [Indexed: 03/26/2024] Open
Abstract
Human cytochrome P450 2C19 catalyzes P450 enzyme reactions of various substrates, including steroids and clinical drugs. Recombinant P450 2C19 enzyme with histidine tag was successfully expressed in Escherichia coli and purified using affinity column chromatography. Ultra-performance liquid chromatography-tandem mass (UPLC-MS/MS) spectrometry showed that the purified P450 2C19 enzyme catalyzed 5-hydroxylation reaction of omeprazole. The purified enzyme displayed typical type I binding spectra to progesterone with a Kd value of 4.5 ± 0.2 µM, indicating a tight substrate binding. P450 2C19 catalyzed the hydroxylation of progesterone to produce 21-hydroxy (OH) as a major and 17-OH product as a minor product. Steady-state kinetic analysis of progesterone 21-hydroxylation indicated that the addition of cytochrome b5 stimulated a five-times catalytic turnover number of P450 2C19 with a kcat value of 1.07 ± 0.08 min-1. The molecular docking model of progesterone in the active site of P450 2C19 displayed that the 21-carbon of progesterone was located close to the heme with a distance of 4.7 Å, suggesting 21-hydroxylation of progesterone is the optimal reaction of P450 2C19 enzyme for a productive orientation of the substrate. Our findings will help investigate the extent to which cytochrome b5 affects the metabolism of P450 2C19 to drugs and steroids. Supplementary Information The online version contains supplementary material available at 10.1007/s43188-023-00219-8.
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Affiliation(s)
- Gyu-Hyeong Lee
- Department of Biological Sciences, Konkuk University, 120 Neungdongro, Gwangjjn-Gu, Seoul, 05025 Republic of Korea
| | - Vitchan Kim
- Department of Biological Sciences, Konkuk University, 120 Neungdongro, Gwangjjn-Gu, Seoul, 05025 Republic of Korea
| | - Sung-Gyu Lee
- Department of Biological Sciences, Konkuk University, 120 Neungdongro, Gwangjjn-Gu, Seoul, 05025 Republic of Korea
| | - Eunseo Jeong
- Department of Biological Sciences, Konkuk University, 120 Neungdongro, Gwangjjn-Gu, Seoul, 05025 Republic of Korea
| | - Changmin Kim
- Department of Biological Sciences, Konkuk University, 120 Neungdongro, Gwangjjn-Gu, Seoul, 05025 Republic of Korea
| | - Yoo-Bin Lee
- Department of Biological Sciences, Konkuk University, 120 Neungdongro, Gwangjjn-Gu, Seoul, 05025 Republic of Korea
| | - Donghak Kim
- Department of Biological Sciences, Konkuk University, 120 Neungdongro, Gwangjjn-Gu, Seoul, 05025 Republic of Korea
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2
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Abstract
There are many factors which are known to cause variability in human in vitro enzyme kinetic data. Factors such as the source of enzyme and how it was prepared, the genetics and background of the donor, how the in vitro studies are designed, and how the data are analyzed contribute to variability in the resulting kinetic parameters. It is important to consider not only the factors which cause variability within an experiment, such as selection of a probe substrate, but also those that cause variability when comparing kinetic data across studies and laboratories. For example, the artificial nature of the microsomal lipid membrane and microenvironment in some recombinantly expressed enzymes, relative to those found in native tissue microsomes, has been shown to influence enzyme activity and thus can be a source of variability when comparing across the two different systems. All of these factors, and several others, are discussed in detail in the chapter below. In addition, approaches which can be used to visualize the uncertainty arising from the use of enzyme kinetic data within the context of predicting human pharmacokinetics are discussed.
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Gutiérrez-García L, Arró M, Altabella T, Ferrer A, Boronat A. Structural and functional analysis of tomato sterol C22 desaturase. BMC PLANT BIOLOGY 2021; 21:141. [PMID: 33731007 PMCID: PMC7972189 DOI: 10.1186/s12870-021-02898-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 02/21/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND Sterols are structural and functional components of eukaryotic cell membranes. Plants produce a complex mixture of sterols, among which β-sitosterol, stigmasterol, campesterol, and cholesterol in some Solanaceae, are the most abundant species. Many reports have shown that the stigmasterol to β-sitosterol ratio changes during plant development and in response to stresses, suggesting that it may play a role in the regulation of these processes. In tomato (Solanum lycopersicum), changes in the stigmasterol to β-sitosterol ratio correlate with the induction of the only gene encoding sterol C22-desaturase (C22DES), the enzyme specifically involved in the conversion of β-sitosterol to stigmasterol. However, despite the biological interest of this enzyme, there is still a lack of knowledge about several relevant aspects related to its structure and function. RESULTS In this study we report the subcellular localization of tomato C22DES in the endoplasmic reticulum (ER) based on confocal fluorescence microscopy and cell fractionation analyses. Modeling studies have also revealed that C22DES consists of two well-differentiated domains: a single N-terminal transmembrane-helix domain (TMH) anchored in the ER-membrane and a globular (or catalytic) domain that is oriented towards the cytosol. Although TMH is sufficient for the targeting and retention of the enzyme in the ER, the globular domain may also interact and be retained in the ER in the absence of the N-terminal transmembrane domain. The observation that a truncated version of C22DES lacking the TMH is enzymatically inactive revealed that the N-terminal membrane domain is essential for enzyme activity. The in silico analysis of the TMH region of plant C22DES revealed several structural features that could be involved in substrate recognition and binding. CONCLUSIONS Overall, this study contributes to expand the current knowledge on the structure and function of plant C22DES and to unveil novel aspects related to plant sterol metabolism.
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Affiliation(s)
- Laura Gutiérrez-García
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
| | - Montserrat Arró
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028, Barcelona, Spain
| | - Teresa Altabella
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
- Department of Biology, Healthcare and the Environment, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028, Barcelona, Spain
| | - Albert Ferrer
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028, Barcelona, Spain
| | - Albert Boronat
- Center for Research in Agricultural Genomics (CSIC-IRTA-UAB-UB), Bellaterra, Barcelona, Spain.
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, 08028, Barcelona, Spain.
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Modulation of CYP2C9 activity and hydrogen peroxide production by cytochrome b 5. Sci Rep 2020; 10:15571. [PMID: 32968106 PMCID: PMC7511354 DOI: 10.1038/s41598-020-72284-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 08/28/2020] [Indexed: 11/09/2022] Open
Abstract
Cytochromes P450 (CYP) play a major role in drug detoxification, and cytochrome b5 (cyt b5) stimulates the catalytic cycle of mono-oxygenation and detoxification reactions. Collateral reactions of this catalytic cycle can lead to a significant production of toxic reactive oxygen species (ROS). One of the most abundant CYP isoforms in the human liver is CYP2C9, which catalyzes the metabolic degradation of several drugs including nonsteroidal anti-inflammatory drugs. We studied modulation by microsomal membrane-bound and soluble cyt b5 of the hydroxylation of salicylic acid to gentisic acid and ROS release by CYP2C9 activity in human liver microsomes (HLMs) and by CYP2C9 baculosomes. CYP2C9 accounts for nearly 75% of salicylic acid hydroxylation in HLMs at concentrations reached after usual aspirin doses. The anti-cyt b5 antibody SC9513 largely inhibits the rate of salicylic acid hydroxylation by CYP2C9 in HLMs and CYP2C9 baculosomes, increasing the KM approximately threefold. Besides, soluble human recombinant cyt b5 stimulates the Vmax nearly twofold while it decreases nearly threefold the Km value in CYP2C9 baculosomes. Regarding NADPH-dependent ROS production, soluble recombinant cyt b5 is a potent inhibitor both in HLMs and in CYP2C9 baculosomes, with inhibition constants of 1.04 ± 0.25 and 0.53 ± 0.06 µM cyt b5, respectively. This study indicates that variability in cyt b5 might be a major factor underlying interindividual variability in the metabolism of CYP2C9 substrates.
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5
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A large-scale comparative analysis of affinity, thermodynamics and functional characteristics of interactions of twelve cytochrome P450 isoforms and their redox partners. Biochimie 2019; 162:156-166. [DOI: 10.1016/j.biochi.2019.04.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 04/24/2019] [Indexed: 12/16/2022]
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Yoo SE, Yi M, Kim WY, Cho SA, Lee SS, Lee SJ, Shin JG. Influences of cytochrome b5 expression and its genetic variant on the activity of CYP2C9, CYP2C19 and CYP3A4. Drug Metab Pharmacokinet 2019; 34:201-208. [PMID: 30992242 DOI: 10.1016/j.dmpk.2019.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 03/15/2019] [Accepted: 03/27/2019] [Indexed: 11/28/2022]
Abstract
The objective of the present study was to investigate the effects of cytochrome b5 (cytb5) on the drug metabolism catalyzed by CYP2C9, CYP2C19 and CYP3A4. Activities of CYP2C9, CYP2C19, and CYP3A4 were determined by using the prototypical substrates tolbutamide, omeprazole and midazolam, respectively. Cytb5 protein and mRNA contents showed large inter-individual variations with 11- and 6-fold range, respectively. All of three P450s showed an increased activity in proportion to the amount of cytb5 expression. Particularly, CYP3A4 showed the strongest correlation between cytb5 protein amount and the activity, followed by CYP2C9 and CYP2C19. The putative splicing variant, c.288G>A (rs7238987) was identified and was screened in 36 liver tissues by direct DNA sequencing. Liver tissues having a splicing variant exhibited unexpected sizes of cytb5 mRNA and a decreased expression tendency of cytb5 protein compared to the wild-type. A decreased activity in the metabolism of the CYP2C19 substrate omeprazole was observed in liver tissues carrying the splicing variant when compared to the wild-type Cytb5 (P < 0.05). The present results propose that different expression of cytb5 can cause variations in CYP mediated drug metabolism, which may explain, at least in part, the inter-individual difference in drug responses in addition to the CYP genetic polymorphisms.
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Affiliation(s)
- Sung-Eun Yoo
- Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea
| | - MyeongJin Yi
- Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea
| | - Woo-Young Kim
- Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea
| | - Sun-Ah Cho
- Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea
| | - Sang Seop Lee
- Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea
| | - Su-Jun Lee
- Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.
| | - Jae-Gook Shin
- Department of Pharmacology and PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea; Department of Clinical Pharmacology, Inje University Busan Paik Hospital, Busan, Republic of Korea.
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7
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Different inhibitory effects of azole-containing drugs and pesticides on CYP2C9 polymorphic forms: An in vitro study. Toxicol In Vitro 2018; 50:249-256. [DOI: 10.1016/j.tiv.2018.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 03/30/2018] [Accepted: 04/01/2018] [Indexed: 11/23/2022]
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8
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Simultaneous detection of NADPH consumption and H 2O 2 production using the Ampliflu™ Red assay for screening of P450 activities and uncoupling. Appl Microbiol Biotechnol 2017; 102:985-994. [PMID: 29150709 DOI: 10.1007/s00253-017-8636-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 11/06/2017] [Accepted: 11/07/2017] [Indexed: 10/18/2022]
Abstract
Cytochrome P450s belong to a large and diverse group of heme-containing enzymes. These monooxygenases catalyze the incorporation of a single atom of molecular oxygen into their substrate. In contrast to most other enzymes, the activity of P450 enzymes is not only dependent on substrate and cofactor availability and reaction conditions, but also depends on the coupling efficiency of the catalytic cycle itself. Through the electron transfer from NAD(P)H to the heme-center of the P450, the enzyme becomes activated and binds oxygen. The thereby generated iron-oxygen complex undergoes multiple reductive steps forming different activated oxygen species. These intermediates can decay easily, releasing the reactive oxygen species superoxide anion and hydrogen peroxide (H2O2), which can also be further reduced to water. This so-called uncoupling of the reaction cycle drains electrons from the system, which consequently does not lead to the desired product, but merely H2O2 formation with stoichiometric consumption of NAD(P)H. Hence, measuring NAD(P)H consumption only can lead to an overestimation of substrate conversion. To measure this uncoupling, we herein report a microtiter plate-based assay for the simultaneous quantification of hydrogen peroxide formation and NAD(P)H consumption using Ampliflu™ Red as reporter. This was exemplified for the P450 monooxygenase from Bacillus megaterium (P450 BM3) and five mutants, using different substrates. We demonstrate the applicability of the assay, which provides a versatile basis for a high-throughput preliminary screening of P450 enzyme libraries without the need for GC or HPLC analysis and clear indication of the extent of hydrogen peroxide uncoupling.
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Bhatt MR, Khatri Y, Rodgers RJ, Martin LL. Role of cytochrome b5 in the modulation of the enzymatic activities of cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1). J Steroid Biochem Mol Biol 2017; 170:2-18. [PMID: 26976652 DOI: 10.1016/j.jsbmb.2016.02.033] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 02/25/2016] [Accepted: 02/27/2016] [Indexed: 12/13/2022]
Abstract
Cytochrome b5 (cyt b5) is a small hemoprotein that plays a significant role in the modulation of activities of an important steroidogenic enzyme, cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1, CYP17A1). Located in the zona fasciculata and zona reticularis of the adrenal cortex and in the gonads, P450 17A1 catalyzes two different reactions in the steroidogenic pathway; the 17α-hydroxylation and 17,20-lyase, in the endoplasmic reticulum of these respective tissues. The activities of P450 17A1 are regulated by cyt b5 that enhances the 17,20-lyase reaction by promoting the coupling of P450 17A1 and cytochrome P450 reductase (CPR), allosterically. Cyt b5 can also act as an electron donor to enhance the 16-ene-synthase activity of human P450 17A1. In this review, we discuss the many roles of cyt b5 and focus on the modulation of CYP17A1 activities by cyt b5 and the mechanisms involved.
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Affiliation(s)
- Megh Raj Bhatt
- Everest Biotech Pvt. Ltd., Khumaltar, Lalitpur, P.O. Box 21608, Kathmandu 44600, Nepal
| | - Yogan Khatri
- Institute of Biochemistry, Saarland University, 66123 Saarbrücken, Germany
| | - Raymond J Rodgers
- School of Medicine, Robinson Research Institute, University of Adelaide, Adelaide SA 5005, Australia
| | - Lisandra L Martin
- School of Chemistry, Monash University, Clayton, 3800, Victoria, Australia.
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10
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Barnaba C, Martinez MJ, Taylor E, Barden AO, Brozik JA. Single-Protein Tracking Reveals That NADPH Mediates the Insertion of Cytochrome P450 Reductase into a Biomimetic of the Endoplasmic Reticulum. J Am Chem Soc 2017; 139:5420-5430. [PMID: 28347139 DOI: 10.1021/jacs.7b00663] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cytochrome P450 reductase (CPR) is the redox partner for most human cytochrome P450 enzymes. It is also believed that CPR is an integral membrane protein exclusively. Herein, we report that, contrary to this belief, CPR can exist as a peripheral membrane protein in the absence of NADPH and will transition to an integral membrane protein in the presence of stoichiometric amounts of NADPH or greater. All experiments were performed in a solid-supported cushioned lipid bilayer that closely matched the chemical composition of the human endoplasmic reticulum and served as an ER biomimetic. The phase characteristics and fluidity of the ER biomimetic was characterized with fluorescence micrographs and temperature-dependent fluorescence recovery after photobleaching. The interactions of CPR with the ER biomimetic were directly observed by tracking single CPR molecules using time-lapse single-molecule fluorescence imaging and subsequent analysis of tracks. These studies revealed dramatic changes in diffusion coefficient and the degree of partitioning of CPR as a function of NADPH concentration.
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Affiliation(s)
- Carlo Barnaba
- Department of Chemistry, Washington State University , P.O. Box 644630, Pullman, Washington 99164-4630, United States
| | - Michael J Martinez
- Department of Chemistry, Washington State University , P.O. Box 644630, Pullman, Washington 99164-4630, United States
| | - Evan Taylor
- Department of Chemistry, Washington State University , P.O. Box 644630, Pullman, Washington 99164-4630, United States
| | - Adam O Barden
- Department of Chemistry, Washington State University , P.O. Box 644630, Pullman, Washington 99164-4630, United States
| | - James A Brozik
- Department of Chemistry, Washington State University , P.O. Box 644630, Pullman, Washington 99164-4630, United States
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11
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Challenges in assignment of allosteric effects in cytochrome P450-catalyzed substrate oxidations to structural dynamics in the hemoprotein architecture. J Inorg Biochem 2017; 167:100-115. [DOI: 10.1016/j.jinorgbio.2016.11.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 10/17/2016] [Accepted: 11/22/2016] [Indexed: 12/19/2022]
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12
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Allosteric activation of midazolam CYP3A5 hydroxylase activity by icotinib – Enhancement by ketoconazole. Biochem Pharmacol 2016; 121:67-77. [DOI: 10.1016/j.bcp.2016.09.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 09/15/2016] [Indexed: 11/20/2022]
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13
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Parmentier Y, Pothier C, Delmas A, Caradec F, Trancart MM, Guillet F, Bouaita B, Chesne C, Brian Houston J, Walther B. Direct and quantitative evaluation of the human CYP3A4 contribution (fm) to drug clearance using the in vitro SILENSOMES model. Xenobiotica 2016; 47:562-575. [DOI: 10.1080/00498254.2016.1208854] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Yannick Parmentier
- Biopharmaceutical Research Department, Technologie Servier, Orléans Cedex, France,
| | - Corinne Pothier
- Biopharmaceutical Research Department, Technologie Servier, Orléans Cedex, France,
| | - Audrey Delmas
- Biopharmaceutical Research Department, Technologie Servier, Orléans Cedex, France,
| | - Fabrice Caradec
- Biopharmaceutical Research Department, Technologie Servier, Orléans Cedex, France,
| | | | | | | | | | | | - Bernard Walther
- Biopharmaceutical Research Department, Technologie Servier, Orléans Cedex, France,
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14
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Pan ST, Xue D, Li ZL, Zhou ZW, He ZX, Yang Y, Yang T, Qiu JX, Zhou SF. Computational Identification of the Paralogs and Orthologs of Human Cytochrome P450 Superfamily and the Implication in Drug Discovery. Int J Mol Sci 2016; 17:E1020. [PMID: 27367670 PMCID: PMC4964396 DOI: 10.3390/ijms17071020] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 04/02/2016] [Accepted: 06/07/2016] [Indexed: 12/31/2022] Open
Abstract
The human cytochrome P450 (CYP) superfamily consisting of 57 functional genes is the most important group of Phase I drug metabolizing enzymes that oxidize a large number of xenobiotics and endogenous compounds, including therapeutic drugs and environmental toxicants. The CYP superfamily has been shown to expand itself through gene duplication, and some of them become pseudogenes due to gene mutations. Orthologs and paralogs are homologous genes resulting from speciation or duplication, respectively. To explore the evolutionary and functional relationships of human CYPs, we conducted this bioinformatic study to identify their corresponding paralogs, homologs, and orthologs. The functional implications and implications in drug discovery and evolutionary biology were then discussed. GeneCards and Ensembl were used to identify the paralogs of human CYPs. We have used a panel of online databases to identify the orthologs of human CYP genes: NCBI, Ensembl Compara, GeneCards, OMA ("Orthologous MAtrix") Browser, PATHER, TreeFam, EggNOG, and Roundup. The results show that each human CYP has various numbers of paralogs and orthologs using GeneCards and Ensembl. For example, the paralogs of CYP2A6 include CYP2A7, 2A13, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 2F1, 2J2, 2R1, 2S1, 2U1, and 2W1; CYP11A1 has 6 paralogs including CYP11B1, 11B2, 24A1, 27A1, 27B1, and 27C1; CYP51A1 has only three paralogs: CYP26A1, 26B1, and 26C1; while CYP20A1 has no paralog. The majority of human CYPs are well conserved from plants, amphibians, fishes, or mammals to humans due to their important functions in physiology and xenobiotic disposition. The data from different approaches are also cross-validated and validated when experimental data are available. These findings facilitate our understanding of the evolutionary relationships and functional implications of the human CYP superfamily in drug discovery.
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Affiliation(s)
- Shu-Ting Pan
- Department of Oral and Maxillofacial Surgery, the First Affiliated Hospital of Nanchang University, Nanchang 330003, China.
| | - Danfeng Xue
- Department of Oral and Maxillofacial Surgery, the First Affiliated Hospital of Nanchang University, Nanchang 330003, China.
| | - Zhi-Ling Li
- Department of Pharmacy, Shanghai Children's Hospital, Shanghai Jiao Tong University, Shanghai 200040, China.
| | - Zhi-Wei Zhou
- Department of Pharmaceutical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA.
| | - Zhi-Xu He
- Guizhou Provincial Key Laboratory for Regenerative Medicine, Stem Cell and Tissue Engineering Research Center & Sino-US Joint Laboratory for Medical Sciences, Guizhou Medical University, Guiyang 550004, China.
| | - Yinxue Yang
- Department of Colorectal Surgery, General Hospital of Ningxia Medical University, Yinchuan 750004, China.
| | - Tianxin Yang
- Department of Internal Medicine, University of Utah and Salt Lake Veterans Affairs Medical Center, Salt Lake City, UT 84132, USA.
| | - Jia-Xuan Qiu
- Department of Oral and Maxillofacial Surgery, the First Affiliated Hospital of Nanchang University, Nanchang 330003, China.
| | - Shu-Feng Zhou
- Department of Chemical and Pharmaceutical Engineering, College of Chemical Engineering, Huaqiao University, Xiamen 361021, Fujian, China.
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15
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Bostick CD, Hickey KM, Wollenberg LA, Flora DR, Tracy TS, Gannett PM. Immobilized Cytochrome P450 for Monitoring of P450-P450 Interactions and Metabolism. ACTA ACUST UNITED AC 2016; 44:741-9. [PMID: 26961240 DOI: 10.1124/dmd.115.067637] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 03/09/2016] [Indexed: 11/22/2022]
Abstract
Cytochrome P450 (P450) protein-protein interactions have been shown to alter their catalytic activity. Furthermore, these interactions are isoform specific and can elicit activation, inhibition, or no effect on enzymatic activity. Studies show that these effects are also dependent on the protein partner cytochrome P450 reductase (CPR) and the order of protein addition to purified reconstituted enzyme systems. In this study, we use controlled immobilization of P450s to a gold surface to gain a better understanding of P450-P450 interactions between three key drug-metabolizing isoforms (CYP2C9, CYP3A4, and CYP2D6). Molecular modeling was used to assess the favorability of homomeric/heteromeric P450 complex formation. P450 complex formation in vitro was analyzed in real time utilizing surface plasmon resonance. Finally, the effects of P450 complex formation were investigated utilizing our immobilized platform and reconstituted enzyme systems. Molecular modeling shows favorable binding of CYP2C9-CPR, CYP2C9-CYP2D6, CYP2C9-CYP2C9, and CYP2C9-CYP3A4, in rank order.KDvalues obtained via surface plasmon resonance show strong binding, in the nanomolar range, for the above pairs, with CYP2C9-CYP2D6 yielding the lowestKD, followed by CYP2C9-CYP2C9, CYP2C9-CPR, and CYP2C9-CYP3A4. Metabolic incubations show that immobilized CYP2C9 metabolism was activated by homomeric complex formation. CYP2C9 metabolism was not affected by the presence of CYP3A4 with saturating CPR concentrations. CYP2C9 metabolism was activated by CYP2D6 at saturating CPR concentrations in solution but was inhibited when CYP2C9 was immobilized. The order of addition of proteins (CYP2C9, CYP2D6, CYP3A4, and CPR) influenced the magnitude of inhibition for CYP3A4 and CYP2D6. These results indicate isoform-specific P450 interactions and effects on P450-mediated metabolism.
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Affiliation(s)
- Chris D Bostick
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia (C.D.B., K.M.H.); Array BioPharma, Boulder, Colorado (L.A.W.); Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (D.R.F.); College of Pharmacy, University of Kentucky, Lexington, Kentucky (T.S.T.); and Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Ft. Lauderdale, Florida (P.M.G.)
| | - Katherine M Hickey
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia (C.D.B., K.M.H.); Array BioPharma, Boulder, Colorado (L.A.W.); Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (D.R.F.); College of Pharmacy, University of Kentucky, Lexington, Kentucky (T.S.T.); and Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Ft. Lauderdale, Florida (P.M.G.)
| | - Lance A Wollenberg
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia (C.D.B., K.M.H.); Array BioPharma, Boulder, Colorado (L.A.W.); Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (D.R.F.); College of Pharmacy, University of Kentucky, Lexington, Kentucky (T.S.T.); and Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Ft. Lauderdale, Florida (P.M.G.)
| | - Darcy R Flora
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia (C.D.B., K.M.H.); Array BioPharma, Boulder, Colorado (L.A.W.); Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (D.R.F.); College of Pharmacy, University of Kentucky, Lexington, Kentucky (T.S.T.); and Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Ft. Lauderdale, Florida (P.M.G.)
| | - Timothy S Tracy
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia (C.D.B., K.M.H.); Array BioPharma, Boulder, Colorado (L.A.W.); Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (D.R.F.); College of Pharmacy, University of Kentucky, Lexington, Kentucky (T.S.T.); and Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Ft. Lauderdale, Florida (P.M.G.)
| | - Peter M Gannett
- Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia (C.D.B., K.M.H.); Array BioPharma, Boulder, Colorado (L.A.W.); Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota (D.R.F.); College of Pharmacy, University of Kentucky, Lexington, Kentucky (T.S.T.); and Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Ft. Lauderdale, Florida (P.M.G.)
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16
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Guo J, Thiess S, Johansson I, Mkrtchian S, Ingelman-Sundberg M. Membrane topology and search for potential redox partners of colon cancer-specific cytochrome P450 2W1. FEBS Lett 2016; 590:330-9. [PMID: 26787547 DOI: 10.1002/1873-3468.12063] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 12/16/2015] [Accepted: 12/16/2015] [Indexed: 01/26/2023]
Abstract
Cytochrome P450 2W1 (CYP2W1) is a colon tumor-specific enzyme, suggested as a potential target for cancer therapy. In contrast to other endoplasmic reticulum P450s, we found completely inverted ER membrane topology of CYP2W1 using different approaches (redox sensitive luciferase assay and protease protection assay) and demonstrated that canonical CYP reductants, cytochrome P450 reductase, and cytochrome b5 cannot serve as electron donors for CYP2W1. Moreover, the reduced catalytic activity of the Asn177 mutant that is modified by glycan moieties in the wild-type enzyme indicates a functional relevance of CYP2W1 glycosylation.
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Affiliation(s)
- Jia Guo
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Stefanie Thiess
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Inger Johansson
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Souren Mkrtchian
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Magnus Ingelman-Sundberg
- Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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17
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Manoj KM, Gade SK, Venkatachalam A, Gideon DA. Electron transfer amongst flavo- and hemo-proteins: diffusible species effect the relay processes, not protein–protein binding. RSC Adv 2016. [DOI: 10.1039/c5ra26122h] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Reductase reduces cytochrome cviarelays of highly mobile diffusible agents; not by direct binding and inter-protein long-distance electron tunnelling.
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Affiliation(s)
| | - Sudeep K. Gade
- Hemoproteins Lab
- School of Biosciences and Technology
- VIT University
- Vellore
- India-632014
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18
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He ZX, Chen XW, Zhou ZW, Zhou SF. Impact of physiological, pathological and environmental factors on the expression and activity of human cytochrome P450 2D6 and implications in precision medicine. Drug Metab Rev 2015; 47:470-519. [PMID: 26574146 DOI: 10.3109/03602532.2015.1101131] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
With only 1.3-4.3% in total hepatic CYP content, human CYP2D6 can metabolize more than 160 drugs. It is a highly polymorphic enzyme and subject to marked inhibition by a number of drugs, causing a large interindividual variability in drug clearance and drug response and drug-drug interactions. The expression and activity of CYP2D6 are regulated by a number of physiological, pathological and environmental factors at transcriptional, post-transcriptional, translational and epigenetic levels. DNA hypermethylation and histone modifications can repress the expression of CYP2D6. Hepatocyte nuclear factor-4α binds to a directly repeated element in the promoter of CYP2D6 and thus regulates the expression of CYP2D6. Small heterodimer partner represses hepatocyte nuclear factor-4α-mediated transactivation of CYP2D6. GW4064, a farnesoid X receptor agonist, decreases hepatic CYP2D6 expression and activity while increasing small heterodimer partner expression and its recruitment to the CYP2D6 promoter. The genotypes are key determinants of interindividual variability in CYP2D6 expression and activity. Recent genome-wide association studies have identified a large number of genes that can regulate CYP2D6. Pregnancy induces CYP2D6 via unknown mechanisms. Renal or liver diseases, smoking and alcohol use have minor to moderate effects only on CYP2D6 activity. Unlike CYP1 and 3 and other CYP2 members, CYP2D6 is resistant to typical inducers such as rifampin, phenobarbital and dexamethasone. Post-translational modifications such as phosphorylation of CYP2D6 Ser135 have been observed, but the functional impact is unknown. Further functional and validation studies are needed to clarify the role of nuclear receptors, epigenetic factors and other factors in the regulation of CYP2D6.
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Affiliation(s)
- Zhi-Xu He
- a Guizhou Provincial Key Laboratory for Regenerative Medicine, Stem Cell and Tissue Engineering Research Center & Sino-US Joint Laboratory for Medical Sciences, Guizhou Medical University , Guiyang , Guizhou , China
| | - Xiao-Wu Chen
- b Department of General Surgery , The First People's Hospital of Shunde, Southern Medical University , Shunde , Foshan , Guangdong , China , and
| | - Zhi-Wei Zhou
- c Department of Pharmaceutical Science , College of Pharmacy, University of South Florida , Tampa , FL , USA
| | - Shu-Feng Zhou
- a Guizhou Provincial Key Laboratory for Regenerative Medicine, Stem Cell and Tissue Engineering Research Center & Sino-US Joint Laboratory for Medical Sciences, Guizhou Medical University , Guiyang , Guizhou , China .,c Department of Pharmaceutical Science , College of Pharmacy, University of South Florida , Tampa , FL , USA
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19
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Miyauchi Y, Nagata K, Yamazoe Y, Mackenzie PI, Yamada H, Ishii Y. Suppression of Cytochrome P450 3A4 Function by UDP-Glucuronosyltransferase 2B7 through a Protein-Protein Interaction: Cooperative Roles of the Cytosolic Carboxyl-Terminal Domain and the Luminal Anchoring Region. Mol Pharmacol 2015; 88:800-12. [PMID: 26243732 DOI: 10.1124/mol.115.098582] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 07/31/2015] [Indexed: 12/13/2022] Open
Abstract
There is a large discrepancy between the interindividual difference in the hepatic expression level of cytochrome P450 3A4 (CYP3A4) and that of drug clearance mediated by this enzyme. However, the reason for this discrepancy remains largely unknown. Because CYP3A4 interacts with UDP-glucuronosyltransferase 2B7 (UGT2B7) to alter its function, the reverse regulation is expected to modulate CYP3A4-catalyzed activity. To address this issue, we investigated whether protein-protein interaction between CYP3A4 and UGT2B7 modulates CYP3A4 function. For this purpose, we coexpressed CYP3A4, NADPH-cytochrome P450 reductase, and UGT2B7 using a baculovirus-insect cell system. The activity of CYP3A4 was significantly suppressed by coexpressing UGT2B7, and this suppressive effect was lost when UGT2B7 was replaced with calnexin (CNX). These results strongly suggest that UGT2B7 negatively regulates CYP3A4 activity through a protein-protein interaction. To identify the UGT2B7 domain associated with CYP3A4 suppression we generated 12 mutants including chimeras with CNX. Mutations introduced into the UGT2B7 carboxyl-terminal transmembrane helix caused a loss of the suppressive effect on CYP3A4. Thus, this hydrophobic region is necessary for the suppression of CYP3A4 activity. Replacement of the hydrophilic end of UGT2B7 with that of CNX produced a similar suppressive effect as the native enzyme. The data using chimeric protein demonstrated that the internal membrane-anchoring region of UGT2B7 is also needed for the association with CYP3A4. These data suggest that 1) UGT2B7 suppresses CYP3A4 function, and 2) both hydrophobic domains located near the C terminus and within UGT2B7 are needed for interaction with CYP3A4.
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Affiliation(s)
- Yuu Miyauchi
- Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan (Y.M., H.Y., Y.I.); Tohoku Pharmaceutical University, Sendai, Japan (K.N.); Food Safety Commission, Cabinet Office, Government of Japan, Tokyo, Japan (Y.Y.); and Department of Clinical Pharmacology, Flinders Medical Center and Flinders University, Adelaide, Australia (P.I.M.)
| | - Kiyoshi Nagata
- Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan (Y.M., H.Y., Y.I.); Tohoku Pharmaceutical University, Sendai, Japan (K.N.); Food Safety Commission, Cabinet Office, Government of Japan, Tokyo, Japan (Y.Y.); and Department of Clinical Pharmacology, Flinders Medical Center and Flinders University, Adelaide, Australia (P.I.M.)
| | - Yasushi Yamazoe
- Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan (Y.M., H.Y., Y.I.); Tohoku Pharmaceutical University, Sendai, Japan (K.N.); Food Safety Commission, Cabinet Office, Government of Japan, Tokyo, Japan (Y.Y.); and Department of Clinical Pharmacology, Flinders Medical Center and Flinders University, Adelaide, Australia (P.I.M.)
| | - Peter I Mackenzie
- Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan (Y.M., H.Y., Y.I.); Tohoku Pharmaceutical University, Sendai, Japan (K.N.); Food Safety Commission, Cabinet Office, Government of Japan, Tokyo, Japan (Y.Y.); and Department of Clinical Pharmacology, Flinders Medical Center and Flinders University, Adelaide, Australia (P.I.M.)
| | - Hideyuki Yamada
- Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan (Y.M., H.Y., Y.I.); Tohoku Pharmaceutical University, Sendai, Japan (K.N.); Food Safety Commission, Cabinet Office, Government of Japan, Tokyo, Japan (Y.Y.); and Department of Clinical Pharmacology, Flinders Medical Center and Flinders University, Adelaide, Australia (P.I.M.)
| | - Yuji Ishii
- Laboratory of Molecular Life Sciences, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan (Y.M., H.Y., Y.I.); Tohoku Pharmaceutical University, Sendai, Japan (K.N.); Food Safety Commission, Cabinet Office, Government of Japan, Tokyo, Japan (Y.Y.); and Department of Clinical Pharmacology, Flinders Medical Center and Flinders University, Adelaide, Australia (P.I.M.)
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20
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Storbeck KH, Swart AC, Fox CL, Swart P. Cytochrome b5 modulates multiple reactions in steroidogenesis by diverse mechanisms. J Steroid Biochem Mol Biol 2015; 151:66-73. [PMID: 25446886 DOI: 10.1016/j.jsbmb.2014.11.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 11/02/2014] [Accepted: 11/21/2014] [Indexed: 12/18/2022]
Abstract
Cytochrome b5 (cyt-b5) is a relatively small haemoprotein which plays an important role in the regulation of mammalian steroidogenesis. This unique protein has the ability to modulate the activity of key steroidogenic enzymes via a number of diverse reaction mechanisms. Cyt-b5 can augment the 17,20-lyase activity of CYP17A1 by promoting the interaction of CYP17A1 and POR; enhance the 16-ene-synthase activity of CYP17A1 by acting as an electron donor; and enhance the activity of 3βHSD by increasing the affinity of 3βHSD for its cofactor NAD(+). We review the modulation of CYP17A1 and 3βHSD activity by cyt-b5 and discuss the reaction mechanisms associated with each activity. The physiological importance of cyt-b5 in regulating mammalian steroidogenesis is presented and the impact of inactivating cyt-b5 mutations are reviewed. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.
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Affiliation(s)
- Karl-Heinz Storbeck
- Department of Biochemistry, University of Stellenbosch, Stellenbosch 7600, South Africa
| | - Amanda C Swart
- Department of Biochemistry, University of Stellenbosch, Stellenbosch 7600, South Africa
| | - Cheryl L Fox
- Department of Biochemistry, University of Stellenbosch, Stellenbosch 7600, South Africa
| | - Pieter Swart
- Department of Biochemistry, University of Stellenbosch, Stellenbosch 7600, South Africa.
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21
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Kandel SE, Lampe JN. Role of protein-protein interactions in cytochrome P450-mediated drug metabolism and toxicity. Chem Res Toxicol 2014; 27:1474-86. [PMID: 25133307 PMCID: PMC4164225 DOI: 10.1021/tx500203s] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
![]()
Through their unique oxidative chemistry,
cytochrome P450 monooxygenases
(CYPs) catalyze the elimination of most drugs and toxins from the
human body. Protein–protein interactions play a critical role
in this process. Historically, the study of CYP–protein interactions
has focused on their electron transfer partners and allosteric mediators,
cytochrome P450 reductase and cytochrome b5. However, CYPs can bind
other proteins that also affect CYP function. Some examples include
the progesterone receptor membrane component 1, damage resistance
protein 1, human and bovine serum albumin, and intestinal fatty acid
binding protein, in addition to other CYP isoforms. Furthermore, disruption
of these interactions can lead to altered paths of metabolism and
the production of toxic metabolites. In this review, we summarize
the available evidence for CYP protein–protein interactions
from the literature and offer a discussion of the potential impact
of future studies aimed at characterizing noncanonical protein–protein
interactions with CYP enzymes.
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Affiliation(s)
- Sylvie E Kandel
- XenoTech, LLC , 16825 West 116th Street, Lenexa, Kansas 66219, United States
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22
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Ramsden D, Tweedie DJ, Chan TS, Tracy TS. Altered CYP2C9 activity following modulation of CYP3A4 levels in human hepatocytes: an example of protein-protein interactions. Drug Metab Dispos 2014; 42:1940-6. [PMID: 25157098 DOI: 10.1124/dmd.114.057901] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cytochrome P450 (P450) protein-protein interactions resulting in modulation of enzyme activities have been well documented using recombinant isoforms. This interaction has been less clearly demonstrated in a more physiologic in vitro system such as human hepatocytes. As an expansion of earlier work (Subramanian et al., 2010), in which recombinant CYP2C9 activity decreased with increasing levels of CYP3A4, the current study modulated CYP3A4 content in human hepatocytes to determine the impact on CYP2C9. Modulation of CYP3A4 levels in situ was enabled by the use of a long-term human hepatocyte culture model (HepatoPac) shown to retain phenotypic hepatocyte function over a number of weeks. The extended period of culture allowed time for knockdown of CYP3A4 protein by small interfering RNA (siRNA) with subsequent recovery, as well as upregulation through induction with a recovery period. CYP3A4 gene silencing resulted in a 60% decrease in CYP3A4 activity and protein levels with a concomitant 74% increase in CYP2C9 activity, with no change in CYP2C9 mRNA levels. Upon removal of siRNA, both CYP2C9 and CYP3A4 activities returned to pre-knockdown levels. Importantly, modulation of CYP3A4 protein levels had no impact on cytochrome P450 reductase activities or levels. However, the possibility for competition for limiting reductase cannot be ruled out. Interestingly, lowering CYP3A4 levels also increased UDP-glucuronosyltransferase 2B7 activity. These studies clearly demonstrate that alterations in CYP3A4 levels can modulate CYP2C9 activity in situ and suggest that further studies are warranted to evaluate the possible clinical consequences of these findings.
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Affiliation(s)
- Diane Ramsden
- Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharmaceuticals, Ridgefield, Connecticut (D.R., D.J.T., T.S.C.); and Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky (T.S.T.)
| | - Donald J Tweedie
- Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharmaceuticals, Ridgefield, Connecticut (D.R., D.J.T., T.S.C.); and Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky (T.S.T.)
| | - Tom S Chan
- Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharmaceuticals, Ridgefield, Connecticut (D.R., D.J.T., T.S.C.); and Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky (T.S.T.)
| | - Timothy S Tracy
- Drug Metabolism and Pharmacokinetics, Boehringer Ingelheim Pharmaceuticals, Ridgefield, Connecticut (D.R., D.J.T., T.S.C.); and Department of Pharmaceutical Sciences, University of Kentucky, Lexington, Kentucky (T.S.T.)
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23
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Wang YH, Gibson CR. Variability in human in vitro enzyme kinetics. Methods Mol Biol 2014; 1113:337-362. [PMID: 24523120 DOI: 10.1007/978-1-62703-758-7_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
There are many factors which are known to cause variability in human in vitro enzyme kinetic data. Factors such as the source of enzyme and how it was prepared, the genetics and background of the donor, how the in vitro studies are designed, and how the data are analyzed contribute to variability in the resulting kinetic parameters. It is important to consider not only the factors which cause variability within an experiment, such as selection of a probe substrate, but also those that cause variability when comparing kinetic data across studies and laboratories. For example, the artificial nature of the microsomal lipid membrane and microenvironment in some recombinantly expressed enzymes, relative to those found in native tissue microsomes, has been shown to influence enzyme activity and thus can be a source of variability when comparing across the two different systems. All of these factors, and several others, are discussed in detail in the chapter below.
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Affiliation(s)
- Ying-Hong Wang
- Pharmacokinetics, Pharmacodynamics and Drug Metabolism, Merck Research Laboratories, West Point, PA, USA
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24
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The use of immobilized cytochrome P4502C9 in PMMA-based plug flow bioreactors for the production of drug metabolites. Appl Biochem Biotechnol 2013; 172:1293-306. [PMID: 24166101 DOI: 10.1007/s12010-013-0537-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 09/15/2013] [Indexed: 12/17/2022]
Abstract
Cytochrome P450 enzymes play a key role in the metabolism of pharmaceutical agents. To determine metabolite toxicity, it is necessary to obtain P450 metabolites from various pharmaceutical agents. Here, we describe a bioreactor that is made by immobilizing cytochrome P450 2C9 (CYP2C9) to a poly(methyl methacrylate) surface and, as an alternative to traditional chemical synthesis, can be used to biosynthesize P450 metabolites in a plug flow bioreactor. As part of the development of the CYP2C9 bioreactor, we have studied two different methods of attachment: (1) coupling via the N-terminus using N-hydroxysulfosuccinimide 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and (2) using the Ni(II) chelator 1-acetato-4-benzyl-triazacyclononane to coordinate the enzyme to the surface using a C-terminal histidine tag. Additionally, the propensity for metabolite production of the CYP2C9 proof-of-concept bioreactors as a function of enzyme attachment conditions (e.g., time and enzyme concentration) was examined. Our results show that the immobilization of CYP2C9 enzymes to a PMMA surface represents a viable and alternative approach to the preparation of CYP2C9 metabolites for toxicity testing. Furthermore, the basic approach can be adapted to any cytochrome P450 enzyme and in a high-throughput, automated process.
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25
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Blobaum AL, Bridges TM, Byers FW, Turlington ML, Mattmann ME, Morrison RD, Mackie C, Lavreysen H, Bartolomé JM, Macdonald GJ, Steckler T, Jones CK, Niswender CM, Conn PJ, Lindsley CW, Stauffer SR, Daniels JS. Heterotropic activation of the midazolam hydroxylase activity of CYP3A by a positive allosteric modulator of mGlu5: in vitro to in vivo translation and potential impact on clinically relevant drug-drug interactions. Drug Metab Dispos 2013; 41:2066-75. [PMID: 24003250 DOI: 10.1124/dmd.113.052662] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Allosteric modulation of G protein-coupled receptors has gained considerable attention in the drug discovery arena because it opens avenues to achieve greater selectivity over orthosteric ligands. We recently identified a series of positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGlu(5)) for the treatment of schizophrenia that exhibited robust heterotropic activation of CYP3A4 enzymatic activity. The prototypical compound from this series, 5-(4-fluorobenzyl)-2-((3-fluorophenoxy)methyl)-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine (VU0448187), was found to activate CYP3A4 to >100% of its baseline intrinsic midazolam (MDZ) hydroxylase activity in vitro; activation was CYP3A substrate specific and mGlu(5) PAM dependent. Additional studies revealed the concentration-dependence of CYP3A activation by VU0448187 in multispecies hepatic and intestinal microsomes and hepatocytes, as well as a diminished effect observed in the presence of ketoconazole. Kinetic analyses of the effect of VU0448187 on MDZ metabolism in recombinant P450 or human liver microsomes resulted in a significant increase in V(max) (minimal change in K(m)) and required the presence of cytochrome b5. The atypical kinetics translated in vivo, as rats receiving an intraperitoneal administration of VU0448187 prior to MDZ treatment demonstrated a significant increase in circulating 1- and 4-hydroxy- midazolam (1-OH-MDZ, 4-OH-MDZ) levels compared with rats administered MDZ alone. The discovery of a potent substrate-selective activator of rodent CYP3A with an in vitro to in vivo translation serves to illuminate the impact of increasing intrinsic enzymatic activity of hepatic and extrahepatic CYP3A in rodents, and presents the basis to build models capable of framing the clinical relevance of substrate-dependent heterotropic activation.
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Affiliation(s)
- Anna L Blobaum
- Drug Metabolism and Pharmacokinetics Laboratory (A.L.B., T.M.B., F.W.B., R.D.M., J.S.D.), Medicinal Chemistry Laboratory (M.L.T., M.E.M., C.W.L., S.R.S.), and Molecular Pharmacology Laboratory (C.K.J., C.M.N., P.J.C.), Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, Tennessee; CREATe ADME/Tox, (C.M.), and Neuroscience (H.L., G.J.M., T.S.), Janssen Research and Development, Beerse, Belgium; and Jarama 75, Toledo, Spain (J.M.B.)
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26
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Storbeck KH, Swart AC, Goosen P, Swart P. Cytochrome b5: novel roles in steroidogenesis. Mol Cell Endocrinol 2013; 371:87-99. [PMID: 23228600 DOI: 10.1016/j.mce.2012.11.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 11/20/2012] [Accepted: 11/20/2012] [Indexed: 11/25/2022]
Abstract
Cytochrome b(5) (cyt-b(5)) is essential for the regulation of steroidogenesis and as such has been implicated in a number of clinical conditions. It is well documented that this small hemoprotein augments the 17,20-lyase activity of cytochrome P450 17α-hydroxylase/17,20-lyase (CYP17A1). Studies have revealed that this augmentation is accomplished by cyt-b(5) enhancing the interaction between cytochrome P450 reductase (POR) and CYP17A1. In this paper we present evidence that cyt-b(5) induces a conformational change in CYP17A1, in addition to facilitating the interaction between CYP17A1 and POR. We also review the recently published finding that cyt-b(5) allosterically augments the activity of 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4) isomerase (3βHSD), a non cytochrome P450 enzyme, by increasing the enzymes affinity for its cofactor, NAD(+). The physiological importance of this finding, in terms of understanding adrenal androstenedione production, is examined. Finally, evidence that cyt-b(5) is able to form homomeric complexes in living cells is presented and discussed.
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Affiliation(s)
- Karl-Heinz Storbeck
- Department of Biochemistry, University of Stellenbosch, Stellenbosch 7602, South Africa
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27
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Li Y, Coller JK, Hutchinson MR, Klein K, Zanger UM, Stanley NJ, Abell AD, Somogyi AA. The CYP2B6*6 allele significantly alters the N-demethylation of ketamine enantiomers in vitro. Drug Metab Dispos 2013; 41:1264-72. [PMID: 23550066 DOI: 10.1124/dmd.113.051631] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Ketamine is primarily metabolized to norketamine by hepatic CYP2B6 and CYP3A4-mediated N-demethylation. However, the relative contribution from each enzyme remains controversial. The CYP2B6*6 allele is associated with reduced enzyme expression and activity that may lead to interindividual variability in ketamine metabolism. We examined the N-demethylation of individual ketamine enantiomers using human liver microsomes (HLMs) genotyped for the CYP2B6*6 allele, insect cell-expressed recombinant CYP2B6 and CYP3A4 enzymes, and COS-1 cell-expressed recombinant CYP2B6.1 and CYP2B6.6 protein variant. Effects of CYP-selective inhibitors on norketamine formation were also determined in HLMs. The two-enzyme Michaelis-Menten model best fitted the HLM kinetic data. The Michaelis-Menten constants (K(m)) for the high-affinity enzyme and the low-affinity enzyme were similar to those for the expressed CYP2B6 and CYP3A4, respectively. The intrinsic clearance for both ketamine enantiomers by the high-affinity enzyme in HLMs with CYP2B6*1/*1 genotype were at least 2-fold and 6-fold higher, respectively, than those for CYP2B6*1/*6 genotype and CYP2B6*6/*6 genotype. The V(max) and K(m) values for CYP2B6.1 were approximately 160 and 70% of those for CYP2B6.6, respectively. N,N'N'-triethylenethiophosphoramide (thioTEPA) (CYP2B6 inhibitor, 25 μM) and the monoclonal antibody against CYP2B6 but not troleandomycin (CYP3A4 inhibitor, 25 μM) or the monoclonal antibody against CYP3A4 inhibited ketamine N-demethylation at clinically relevant concentrations. The degree of inhibition was significantly reduced in HLMs with the CYP2B6*6 allele (gene-dose P < 0.05). These results indicate a major role of CYP2B6 in ketamine N-demethylation in vitro and a significant impact of the CYP2B6*6 allele on enzyme-ketamine binding and catalytic activity.
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Affiliation(s)
- Yibai Li
- Discipline of Pharmacology, The University of Adelaide, South Australia, Australia.
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Zhao C, Gao Q, Roberts AG, Shaffer SA, Doneanu CE, Xue S, Goodlett DR, Nelson SD, Atkins WM. Cross-linking mass spectrometry and mutagenesis confirm the functional importance of surface interactions between CYP3A4 and holo/apo cytochrome b(5). Biochemistry 2012; 51:9488-500. [PMID: 23150942 DOI: 10.1021/bi301069r] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome b(5) (cyt b(5)) is one of the key components in the microsomal cytochrome P450 monooxygenase system. Consensus has not been reached about the underlying mechanism of cyt b(5) modulation of CYP catalysis. Both cyt b(5) and apo b(5) are reported to stimulate the activity of several P450 isoforms. In this study, the surface interactions of both holo and apo b(5) with CYP3A4 were investigated and compared for the first time. Chemical cross-linking coupled with mass spectrometric analysis was used to identify the potential electrostatic interactions between the protein surfaces. Subsequently, the models of interaction of holo/apo b(5) with CYP3A4 were built using the identified interacting sites as constraints. Both cyt b(5) and apo b(5) were predicted to bind to the same groove on CYP3A4 with close contacts to the B-B' loop of CYP3A4, a substrate recognition site. Mutagenesis studies further confirmed that the interacting sites on CYP3A4 (Lys96, Lys127, and Lys421) are functionally important. Mutation of these residues reduced or abolished cyt b(5) binding affinity. The critical role of Arg446 on CYP3A4 in binding to cyt b(5) and/or cytochrome P450 reductase was also discovered. The results indicated that electrostatic interactions on the interface of the two proteins are functionally important. The results indicate that apo b(5) can dock with CYP3A4 in a manner analogous to that of holo b(5), so electron transfer from cyt b(5) is not required for its effects.
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Affiliation(s)
- Chunsheng Zhao
- Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, WA 98195, USA
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Tang T, Zhao C, Feng X, Liu X, Qiu L. Knockdown of several components of cytochrome P450 enzyme systems by RNA interference enhances the susceptibility of Helicoverpa armigera to fenvalerate. PEST MANAGEMENT SCIENCE 2012; 68:1501-11. [PMID: 22689565 DOI: 10.1002/ps.3336] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 03/15/2012] [Accepted: 04/04/2012] [Indexed: 05/03/2023]
Abstract
BACKGROUND The function of cytochrome P450 proteins (P450s) in the metabolism of a variety of compounds by oxidation and reduction is well elucidated, but its interactions with other electron transfer components in the pyrethroid resistance of insect pests have been a mystery for a long time. In previous studies the authors cloned and characterised CYP6B7 and cytochrome b(5) (Cyt-b(5)) in the fenvalerate-resistant HDFR strain of cotton bollworm (Helicoverpa armigera Hübner) and showed that CYP6B7 mRNA was overexpressed and important for resistance to fenvalerate. In the present study, the functional interactions of CYP6B7, NADPH-dependent cytochrome P450 reductase (CPR) and Cyt-b(5) were assessed using RNA interference (RNAi) strategies and monitoring for fenvalerate resistance levels. RESULTS RT-qPCR analyses indicated that the expression levels of CYP6B7, CPR and Cyt-b(5) mRNA were decreased drastically in the midgut of fourth-instar larvae of the H. armigera HDFR strain after corresponding double-stranded RNA (dsRNA) injection, compared with that of the control. The knockdown of CYP6B7, CPR and Cyt-b(5) transcripts was time course dependent during a 12-48 h period after dsRNA injection. At the earlier time points analysed, significant suppression of CYP6B7 mRNA levels was observed in larvae injected with dsCYP6B7-313 as compared with controls, and further suppression was observed in larvae injected with dsCYP6B7-313, dsCPR-403 and dsCyt-b(5) . The injection of dsCYP6B7-313 together with dsCPR-403 and dsCyt-b(5) increased larval susceptibility of the HDFR strain to fenvalerate. CONCLUSION The results demonstrated that silencing of CYP6B7 alone or CYP6B7 together with CPR and/or Cyt-b(5) increased the susceptibility of H. armigera to fenvalerate, suggesting that CYP6B7, CPR and Cyt-b(5) collaboratively participated in enhanced metabolism of fenvalerate and played an important role in the resistance of H. armigera to fenvalerate.
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Affiliation(s)
- Tao Tang
- Key Laboratory of Pesticide Chemistry and Application Technology, Ministry of Agriculture, College of Science, China Agricultural University, Beijing, China
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Storbeck KH, Swart AC, Lombard N, Adriaanse CV, Swart P. Cytochrome b(5) forms homomeric complexes in living cells. J Steroid Biochem Mol Biol 2012; 132:311-21. [PMID: 22878120 DOI: 10.1016/j.jsbmb.2012.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 07/23/2012] [Accepted: 07/25/2012] [Indexed: 11/24/2022]
Abstract
Cytochrome b(5) (cyt-b(5)) is a ubiquitous hemoprotein also associated with microsomal cytochrome P450 17α-hydroxylase/17,20 lyase (CYP17A1). In the steroidogenic pathway CYP17A1 catalyses the metabolism of pregnenolone, yielding both glucocorticoid and androgen precursors. While not affecting the 17α-hydroxylation of pregnenolone, cyt-b(5) augments the 17,20 lyase reaction of 17-hydroxypregnenolone, catalyzing the formation of DHEA, through direct protein-protein interactions. In this study, multimeric complex formation of cyt-b(5) and the possible regulatory role of these complexes were investigated. Cyt-b(5) was isolated from ovine liver and used to raise anti-sheep cyt-b(5) immunoglobulins. Immunochemical studies revealed that, in vivo, cyt-b(5) is primarily found in the tetrameric form. Subsequent fluorescent resonance energy transfer (FRET) studies in COS-1 cells confirmed the formation of homomeric complexes by cyt-b(5) in live cells. Site-directed mutagenesis revealed that the C-terminal linker domain of cyt-b(5) is vital for complex formation. The 17,20-lyase activity of CYP17 was augmented by truncated cyt-b(5), which is unable to form complexes when co-expressed in COS-1 cells, thereby implicating the monomeric form of cyt-b(5) as the active species. This study has shown for the first time that cyt-b(5) forms homomeric complexes in vivo, implicating complex formation as a possible regulatory mechanism in steroidogenesis.
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Affiliation(s)
- Karl-Heinz Storbeck
- Department of Biochemistry, University of Stellenbosch, Stellenbosch 7600, South Africa
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31
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Cali JJ, Ma D, Wood MG, Meisenheimer PL, Klaubert DH. Bioluminescent assays for ADME evaluation: dialing in CYP selectivity with luminogenic substrates. Expert Opin Drug Metab Toxicol 2012; 8:1115-30. [DOI: 10.1517/17425255.2012.695345] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Lee SJ, Goldstein JA. Comparison of CYP3A4 and CYP3A5: The Effects of Cytochrome b5 and NADPH-cytochrome P450 Reductase on Testosterone Hydroxylation Activities. Drug Metab Pharmacokinet 2012; 27:663-7. [DOI: 10.2133/dmpk.dmpk-12-sh-030] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Crewe HK, Barter ZE, Yeo KR, Rostami-Hodjegan A. Are there differences in the catalytic activity per unit enzyme of recombinantly expressed and human liver microsomal cytochrome P450 2C9? A systematic investigation into inter-system extrapolation factors. Biopharm Drug Dispos 2011; 32:303-18. [PMID: 21725985 DOI: 10.1002/bdd.760] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 05/02/2011] [Accepted: 05/05/2011] [Indexed: 11/07/2022]
Abstract
The 'relative activity factor' (RAF) compares the activity per unit of microsomal protein in recombinantly expressed cytochrome P450 enzymes (rhCYP) and human liver without separating the potential sources of variation (i.e. abundance of enzyme per mg of protein or variation of activity per unit enzyme). The dimensionless 'inter-system extrapolation factor' (ISEF) dissects differences in activity from those in CYP abundance. Detailed protocols for the determination of this scalar, which is used in population in vitro-in vivo extrapolation (IVIVE), are currently lacking. The present study determined an ISEF for CYP2C9 and, for the first time, systematically evaluated the effects of probe substrate, cytochrome b5 and methods for assessing the intrinsic clearance (CL(int) ). Values of ISEF for S-warfarin, tolbutamide and diclofenac were 0.75 ± 0.18, 0.57 ± 0.07 and 0.37 ± 0.07, respectively, using CL(int) values derived from the kinetic values V(max) and K(m) of metabolite formation in rhCYP2C9 + reductase + b5 BD Supersomes™. The ISEF values obtained using rhCYP2C9 + reductase BD Supersomes™ were more variable, with values of 7.16 ± 1.25, 0.89 ± 0.52 and 0.50 ± 0.05 for S-warfarin, tolbutamide and diclofenac, respectively. Although the ISEF values obtained from rhCYP2C9 + reductase + b5 for the three probe substrates were statistically different (p < 0.001), the use of the mean value of 0.54 resulted in predicted oral clearance values for all three substrates within 1.4 fold of the observed literature values. For consistency in the relative activity across substrates, use of a b5 expressing recombinant system, with the intrinsic clearance calculated from full kinetic data is recommended for generation of the CYP2C9 ISEF. Furthermore, as ISEFs have been found to be sensitive to differences in accessory proteins, rhCYP system specific ISEFs are recommended.
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Affiliation(s)
- H K Crewe
- Academic Unit of Clinical Pharmacology, University of Sheffield, Royal Hallamshire Hospital, Sheffield, UK
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Kaspera R, Naraharisetti SB, Evangelista EA, Marciante KD, Psaty BM, Totah RA. Drug metabolism by CYP2C8.3 is determined by substrate dependent interactions with cytochrome P450 reductase and cytochrome b5. Biochem Pharmacol 2011; 82:681-91. [PMID: 21726541 DOI: 10.1016/j.bcp.2011.06.027] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 06/16/2011] [Accepted: 06/16/2011] [Indexed: 01/20/2023]
Abstract
Genetic polymorphisms in CYP2C8 can influence the metabolism of important therapeutic agents and cause interindividual variation in drug response and toxicity. The significance of the variant CYP2C8*3 has been controversial with reports of higher in vivo but lower in vitro activity compared to CYP2C8*1. In this study, the contribution of the redox partners cytochrome P450 reductase (CPR) and cytochrome b5 to the substrate dependent activity of CYP2C8.3 (R139K, K399R) was investigated in human liver microsomes (HLMs) and Escherichia coli expressed recombinant CYP2C8 proteins using amodiaquine, paclitaxel, rosiglitazone and cerivastatin as probe substrates. For recombinant CYP2C8.3, clearance values were two- to five-fold higher compared to CYP2C8.1. CYP2C8.3's higher k(cat) seems to be dominated by a higher, but substrate specific affinity, towards cytochrome b5 and CPR (K(D) and K(m,red)) which resulted in increased reaction coupling. A stronger binding affinity of ligands to CYP2C8.3, based on a two site binding model, in conjunction with a five fold increase in amplitude of heme spin change during binding of ligands and redox partners could potentially contribute to a higher k(cat). In HLMs, carriers of the CYP2C8*1/*3 genotype were as active as CYP2C8*1/*1 towards the CYP2C8 specific reaction amodiaquine N-deethylation. Large excess of cytochrome b5 compared to CYP2C8 in recombinant systems and HLMs inhibited metabolic clearance, diminishing the difference in k(cat) between the two enzymes, and may provide an explanation for the discrepancy to in vivo data. In silico studies illustrate the genetic differences between wild type and variant on the molecular level.
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Affiliation(s)
- Rüdiger Kaspera
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USA
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Davydov DR. Microsomal monooxygenase as a multienzyme system: the role of P450-P450 interactions. Expert Opin Drug Metab Toxicol 2011; 7:543-58. [PMID: 21395496 DOI: 10.1517/17425255.2011.562194] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION There is increasing evidence of physical interactions (association) among cytochromes P450 in the membranes of the endoplasmic reticulum. Functional consequences of these interactions are often underestimated. AREAS COVERED This article provides a comprehensive overview of available experimental material regarding P450-P450 interactions. Special emphasis is given to the interactions between different P450 species and to the functional consequences of homo- and heterooligomerization. EXPERT OPINION Recent advances provide conclusive evidence for a substantial degree of P450 oligomerization in membranes. Interactions between different P450 species resulting in the formation of mixed oligomers with altered activity and substrate specificity have been demonstrated clearly. There are important indications that oligomerization impedes electron flow to a fraction of the P450 population, which renders some P450 species nonfunctional. Functional consequences of P450-P450 interactions make the integrated properties of the microsomal monooxygenase remarkably different from a simple summation of the properties of the individual P450 species. This complexity compromises the predictive power of the current in vitro models of drug metabolism and warrants an urgent need for development of new model systems that consider the interactions of multiple P450 species.
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Affiliation(s)
- Dmitri R Davydov
- University of California - San Diego, Skaggs School of Pharmacy and Pharmaceutical Sciences, La Jolla, CA 92093, USA.
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Regulation of hemocytes in Drosophila requires dappled cytochrome b5. Biochem Genet 2011; 49:329-51. [PMID: 21279680 PMCID: PMC3092937 DOI: 10.1007/s10528-010-9411-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Accepted: 12/20/2010] [Indexed: 12/12/2022]
Abstract
A major category of mutant hematopoietic phenotypes in Drosophila is melanotic tumors or nodules, which consist of abnormal and overproliferated blood cells, similar to granulomas. Our analyses of the melanotic mutant dappled have revealed a novel type of gene involved in blood cell regulation. The dappled gene is an essential gene that encodes cytochrome b5, a conserved hemoprotein that participates in electron transfer in multiple biochemical reactions and pathways. Viable mutations of dappled cause melanotic nodules and hemocyte misregulation during both hematopoietic waves of development. The sexes are similarly affected, but hemocyte number is different in females and males of both mutants and wild type. Additionally, initial tests show that curcumin enhances the dappled melanotic phenotype and establish screening of endogenous and xenobiotic compounds as a route for analysis of cytochrome b5 function. Overall, dappled provides a tractable genetic model for cytochrome b5, which has been difficult to study in higher organisms.
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Subramanian M, Tam H, Zheng H, Tracy TS. CYP2C9-CYP3A4 protein-protein interactions: role of the hydrophobic N terminus. Drug Metab Dispos 2010; 38:1003-9. [PMID: 20215413 DOI: 10.1124/dmd.109.030155] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cytochromes P450 (P450s) interact with redox transfer proteins, including P450 reductase (CPR) and cytochrome b(5) (b5), all being membrane-bound. In multiple in vitro systems, P450-P450 interactions also have been observed, resulting in alterations in enzymatic activity. The current work investigated the effects and mechanisms of interaction between CYP2C9 and CYP3A4 in a reconstituted system. CYP2C9-mediated metabolism of S-naproxen and S-flurbiprofen was inhibited up to 80% by coincubation with CYP3A4, although K(m) values were unchanged. Increasing CYP3A4 concentrations increased the degree of inhibition, whereas increasing CPR concentrations resulted in less inhibition. Addition of b5 only marginally affected the magnitude of inhibition. In contrast, CYP2C9 did not alter the CYP3A4-mediated metabolism of testosterone. The potential role of the hydrophobic N terminus on these interactions was assessed by incubating truncated CYP2C9 with full-length CYP3A4, and vice versa. In both cases, the inhibition was fully abolished, indicating an important role for hydrophobic forces in CYP2C9-CYP3A4 interactions. Finally, a CYP2C9/CYP3A4 heteromer complex was isolated by coimmunoprecipitation techniques, confirming the physical interaction of the proteins. These results show that the N-terminal membrane binding domains of CYP2C9 and CYP3A4 are involved in heteromer complex formation and that at least one consequence is a reduction in CYP2C9 activity.
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Affiliation(s)
- Murali Subramanian
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, MN 55126, USA
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Subramanian M, Low M, Locuson CW, Tracy TS. CYP2D6-CYP2C9 protein-protein interactions and isoform-selective effects on substrate binding and catalysis. Drug Metab Dispos 2009; 37:1682-9. [PMID: 19448135 DOI: 10.1124/dmd.109.026500] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cytochrome P450 (P450) protein-protein interactions have been observed with various in vitro systems. It is interesting to note that these interactions seem to be isoform-dependent, with some combinations producing no effect and others producing increased or decreased catalytic activity. With some exceptions, most of the work to date has involved P450s from rabbit, rat, and other animal species, with few studies including human P450s. In the studies presented herein, the interactions of two key drug-metabolizing enzymes, CYP2C9 and CYP2D6, were analyzed in a purified, reconstituted enzyme system for changes in both substrate-binding affinity and rates of catalysis. In addition, an extensive study was conducted as to the "order of mixing" for the reconstituted enzyme system and the impact on the observations. CYP2D6 coincubation inhibited CYP2C9-mediated (S)-flurbiprofen metabolism in a protein concentration-dependent manner. V(max) values were reduced by up to 50%, but no appreciable effect on K(m) was observed. Spectral binding studies revealed a 20-fold increase in the K(S) of CYP2C9 toward (S)-flurbiprofen in the presence of CYP2D6. CYP2C9 coincubation had no effect on CYP2D6-mediated dextromethorphan O-demethylation. The order of combination of the proteins (CYP2C9, CYP2D6, and cytochrome P450 reductase) influenced the magnitude of catalysis inhibition as well as the ability of increased cytochrome P450 reductase to attenuate the change in activity. A simple model, congruent with current results and those of others, is proposed to explain oligomer formation. In summary, CYP2C9-CYP2D6 interactions can alter catalytic activity and, thus, influence in vitro-in vivo correlation predictions.
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Affiliation(s)
- Murali Subramanian
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, 308 Harvard Street SE, Minneapolis, MN 55126, USA.
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DiMaio Knych H, DeStefano Shields C, Buckpitt A, Stanley S. Equine cytochrome P450 2C92: cDNA cloning, expression and initial characterization. Arch Biochem Biophys 2009; 485:49-55. [DOI: 10.1016/j.abb.2009.02.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 02/11/2009] [Accepted: 02/12/2009] [Indexed: 12/12/2022]
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Zhang H, Hamdane D, Im SC, Waskell L. Cytochrome b5 Inhibits Electron Transfer from NADPH-Cytochrome P450 Reductase to Ferric Cytochrome P450 2B4. J Biol Chem 2008; 283:5217-25. [DOI: 10.1074/jbc.m709094200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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