1
|
Yamoune S, Müller JP, Langmia IM, Scholl C, Stingl JC. Uncoupling of Cytochrome P450 2B6 and stimulation of reactive oxygen species production in pharmacogenomic alleles affected by interethnic variability. Biochim Biophys Acta Gen Subj 2024; 1868:130595. [PMID: 38467309 DOI: 10.1016/j.bbagen.2024.130595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 02/29/2024] [Accepted: 03/04/2024] [Indexed: 03/13/2024]
Abstract
Cytochrome P450 mediated substrate metabolism is generally characterized by the formation of reactive intermediates. In vitro and in vivo reaction uncoupling, results in the accumulation and dissociation of reactive intermediates, leading to increased ROS formation. The susceptibility towards uncoupling and altered metabolic activity is partly modulated by pharmacogenomic alleles resulting in amino acid substitutions. A large variability in the prevalence of these alleles has been demonstrated in CYP2B6, with some being predominantly unique to African populations. The aim of this study is to characterize the uncoupling potential of recombinant CYP2B6*1, CYP2B6*6 and CYP2B6*34 metabolism of specific substrates. Therefore, functional effects of these alterations on enzyme activity were determined by quantification of bupropion, efavirenz and ketamine biotransformation using HPLC-MS/MS. Determination of H2O2 levels was performed by the AmplexRed/horseradish peroxidase assay. Our studies of the amino acid substitutions Q172H, K262R and R487S revealed an exclusive use of the peroxide shunt for the metabolism of bupropion and ketamine by CYP2B6*K262R. Ketamine was also identified as a trigger for the peroxide shunt in CYP2B6*1 and all variants. Concurrently, ketamine acted as an uncoupler for all enzymes. We further showed that the expressed CYP2B6*34 allele results in the highest H2O2 formation. We therefore conclude that the reaction uncoupling and peroxide shunt are directly linked and can be substrate specifically induced with K262R carriers being most likely to use the peroxide shunt and R487S carrier being most prone to reaction uncoupling. This elucidates the functional diversity of pharmacogenomics in drug metabolism and safety.
Collapse
Affiliation(s)
- Sabrina Yamoune
- Institute of Clinical Pharmacology, University Hospital of RWTH Aachen, Germany; Research Division, Federal Institute for Drugs and Medical Devices (BfArM), Bonn, Germany.
| | - Julian Peter Müller
- Institute of Clinical Pharmacology, University Hospital of RWTH Aachen, Germany
| | | | - Catharina Scholl
- Research Division, Federal Institute for Drugs and Medical Devices (BfArM), Bonn, Germany
| | | |
Collapse
|
2
|
Tan BH, Ahemad N, Pan Y, Palanisamy UD, Othman I, Ong CE. In vitro inhibitory effects of glucosamine, chondroitin and diacerein on human hepatic CYP2D6. Drug Metab Pers Ther 2021; 36:259-270. [PMID: 34821124 DOI: 10.1515/dmpt-2020-0182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Accepted: 03/08/2021] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Glucosamine, chondroitin and diacerein are natural compounds commonly used in treating osteoarthritis. Their concomitant intake may trigger drug-natural product interactions. Cytochrome P450 (CYP) has been implicated in such interactions. Cytochrome P450 2D6 (CYP2D6) is a major hepatic CYP involved in metabolism of 25% of the clinical drugs. This study aimed to investigate the inhibitory effect of these antiarthritic compounds on CYP2D6. METHODS CYP2D6 was heterologously expressed in Escherichia coli. CYP2D6-antiarthritic compound interactions were studied using in vitro enzyme kinetics assay and molecular docking. RESULTS The high-performance liquid chromatography (HPLC)-based dextromethorphan O-demethylase assay was established as CYP2D6 marker. All glucosamines and chondroitins weakly inhibited CYP2D6 (IC50 values >300 µM). Diacerein exhibited moderate inhibition with IC50 and K i values of 34.99 and 38.27 µM, respectively. Its major metabolite, rhein displayed stronger inhibition potencies (IC50=26.22 μM and K i =32.27 μM). Both compounds exhibited mixed-mode of inhibition. In silico molecular dockings further supported data from the in vitro study. From in vitro-in vivo extrapolation, rhein presented an area under the plasma concentration-time curve (AUC) ratio of 1.5, indicating low potential to cause in vivo inhibition. CONCLUSIONS Glucosamine, chondroitin and diacerein unlikely cause clinical interaction with the drug substrates of CYP2D6. Rhein, exhibits only low potential to cause in vivo inhibition.
Collapse
Affiliation(s)
- Boon Hooi Tan
- Division of Applied Biomedical Sciences and Biotechnology, International Medical University, Kuala Lumpur, Malaysia
| | - Nafees Ahemad
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Subang Jaya, Selangor, Malaysia
| | - Yan Pan
- Division of Biomedical Science, University of Nottingham Malaysia Campus, Semenyih, Selangor, Malaysia
| | - Uma Devi Palanisamy
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Subang Jaya, Selangor, Malaysia
| | - Iekhsan Othman
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Subang Jaya, Selangor, Malaysia
| | - Chin Eng Ong
- School of Pharmacy, International Medical University, No. 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000 Kuala Lumpur, Malaysia
| |
Collapse
|
3
|
Tan BH, Ahemad N, Pan Y, Palanisamy UD, Othman I, Ong CE. In vitro inhibitory effects of glucosamine, chondroitin and diacerein on human hepatic CYP2D6. Drug Metab Pers Ther 2021; 0:dmdi-2020-0182. [PMID: 33831979 DOI: 10.1515/dmdi-2020-0182] [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: 11/21/2020] [Accepted: 03/08/2021] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Glucosamine, chondroitin and diacerein are natural compounds commonly used in treating osteoarthritis. Their concomitant intake may trigger drug-natural product interactions. Cytochrome P450 (CYP) has been implicated in such interactions. Cytochrome P450 2D6 (CYP2D6) is a major hepatic CYP involved in metabolism of 25% of the clinical drugs. This study aimed to investigate the inhibitory effect of these antiarthritic compounds on CYP2D6. METHODS CYP2D6 was heterologously expressed in Escherichia coli. CYP2D6-antiarthritic compound interactions were studied using in vitro enzyme kinetics assay and molecular docking. RESULTS The high-performance liquid chromatography (HPLC)-based dextromethorphan O-demethylase assay was established as CYP2D6 marker. All glucosamines and chondroitins weakly inhibited CYP2D6 (IC50 values >300 µM). Diacerein exhibited moderate inhibition with IC50 and K i values of 34.99 and 38.27 µM, respectively. Its major metabolite, rhein displayed stronger inhibition potencies (IC50=26.22 μM and K i =32.27 μM). Both compounds exhibited mixed-mode of inhibition. In silico molecular dockings further supported data from the in vitro study. From in vitro-in vivo extrapolation, rhein presented an area under the plasma concentration-time curve (AUC) ratio of 1.5, indicating low potential to cause in vivo inhibition. CONCLUSIONS Glucosamine, chondroitin and diacerein unlikely cause clinical interaction with the drug substrates of CYP2D6. Rhein, exhibits only low potential to cause in vivo inhibition.
Collapse
Affiliation(s)
- Boon Hooi Tan
- Division of Applied Biomedical Sciences and Biotechnology, International Medical University, Kuala Lumpur, Malaysia
| | - Nafees Ahemad
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Subang Jaya, Selangor, Malaysia
| | - Yan Pan
- Division of Biomedical Science, University of Nottingham Malaysia Campus, Semenyih, Selangor, Malaysia
| | - Uma Devi Palanisamy
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Subang Jaya, Selangor, Malaysia
| | - Iekhsan Othman
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Subang Jaya, Selangor, Malaysia
| | - Chin Eng Ong
- School of Pharmacy, International Medical University, No. 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000Kuala Lumpur, Malaysia
| |
Collapse
|
4
|
Le Daré B, Ferron PJ, Allard PM, Clément B, Morel I, Gicquel T. New insights into quetiapine metabolism using molecular networking. Sci Rep 2020; 10:19921. [PMID: 33199804 PMCID: PMC7669884 DOI: 10.1038/s41598-020-77106-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022] Open
Abstract
Metabolism is involved in both pharmacology and toxicology of most xenobiotics including drugs. Yet, visualization tools facilitating metabolism exploration are still underused, despite the availibility of pertinent bioinformatics solutions. Since molecular networking appears as a suitable tool to explore structurally related molecules, we aimed to investigate its interest in in vitro metabolism exploration. Quetiapine, a widely prescribed antipsychotic drug, undergoes well-described extensive metabolism, and is therefore an ideal candidate for such a proof of concept. Quetiapine was incubated in metabolically competent human liver cell models (HepaRG) for different times (0 h, 3 h, 8 h, 24 h) with or without cytochrom P450 (CYP) inhibitor (ketoconazole as CYP3A4/5 inhibitor and quinidine as CYP2D6 inhibitor), in order to study its metabolism kinetic and pathways. HepaRG culture supernatants were analyzed on an ultra-high performance liquid chromatography coupled with tandem mass spectrometry (LC-HRMS/MS). Molecular networking approach on LC-HRMS/MS data allowed to quickly visualize the quetiapine metabolism kinetics and determine the major metabolic pathways (CYP3A4/5 and/or CYP2D6) involved in metabolite formation. In addition, two unknown putative metabolites have been detected. In vitro metabolite findings were confirmed in blood sample from a patient treated with quetiapine. This is the first report using LC-HRMS/MS untargeted screening and molecular networking to explore in vitro drug metabolism. Our data provide new evidences of the interest of molecular networking in drug metabolism exploration and allow our in vitro model consistency assessment.
Collapse
Affiliation(s)
- Brendan Le Daré
- INSERM, INRAE, CHU Rennes, Institut NuMeCan (Nutrition, Metabolism and Cancer), PREVITOX Network, Univ Rennes, 35033, Rennes, France. .,Forensic Toxicology Laboratory, Rennes University Hospital, 35033, Rennes, France.
| | - Pierre-Jean Ferron
- INSERM, INRAE, CHU Rennes, Institut NuMeCan (Nutrition, Metabolism and Cancer), PREVITOX Network, Univ Rennes, 35033, Rennes, France
| | - Pierre-Marie Allard
- School of Pharmaceutical Sciences, and Institute of Pharmaceutical Sciences of Western Switzerland (ISPSW), University of Geneva, CMU, Rue Michel Servet 1, 1211, Geneva 4, Switzerland
| | - Bruno Clément
- INSERM, INRAE, CHU Rennes, Institut NuMeCan (Nutrition, Metabolism and Cancer), PREVITOX Network, Univ Rennes, 35033, Rennes, France
| | - Isabelle Morel
- INSERM, INRAE, CHU Rennes, Institut NuMeCan (Nutrition, Metabolism and Cancer), PREVITOX Network, Univ Rennes, 35033, Rennes, France.,Forensic Toxicology Laboratory, Rennes University Hospital, 35033, Rennes, France
| | - Thomas Gicquel
- INSERM, INRAE, CHU Rennes, Institut NuMeCan (Nutrition, Metabolism and Cancer), PREVITOX Network, Univ Rennes, 35033, Rennes, France.,Forensic Toxicology Laboratory, Rennes University Hospital, 35033, Rennes, France
| |
Collapse
|
5
|
Heck CS, Seneviratne HK, Bumpus NN. Twelfth-Position Deuteration of Nevirapine Reduces 12-Hydroxy-Nevirapine Formation and Nevirapine-Induced Hepatocyte Death. J Med Chem 2020; 63:6561-6574. [PMID: 32065749 PMCID: PMC7959450 DOI: 10.1021/acs.jmedchem.9b01990] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Indexed: 01/08/2023]
Abstract
Cytochrome P450-dependent metabolism of the anti-HIV drug nevirapine (NVP) to 12-hydroxy-NVP (12-OHNVP) has been implicated in NVP toxicities. We investigated the impact of twelfth-position trideuteration (12-D3NVP) on the hepatic metabolism of and response to NVP. Formation of 12-OHNVP decreased in human (10.6-fold) and mouse (4.6-fold) hepatocytes incubated with 10 μM 12-D3NVP vs NVP. An observed kinetic isotope effect of 10.1 was measured in human liver microsomes. During mouse hepatocyte treatment (400 μM) with NVP or 12-D3NVP, cell death was reduced 30% with 12-D3NVP vs NVP, while glucuronidated and glutathione-conjugated metabolites increased with 12-D3NVP vs NVP. Using mass spectrometry proteomics, changes in hepatocyte protein expression, including an increase in stress marker insulin-like growth factor-binding protein 1 (IGFBP-1), were observed with 12-D3NVP vs NVP. These results demonstrate that while deuteration can reduce P450 metabolite formation, impacts on phase II metabolism and hepatocyte protein expression should be considered when employing deuteration to reduce P450 metabolite-related hepatotoxicity.
Collapse
Affiliation(s)
- Carley
J. S. Heck
- Department
of Pharmacology & Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Herana Kamal Seneviratne
- Department
of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Namandjé N. Bumpus
- Department
of Pharmacology & Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
- Department
of Medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| |
Collapse
|
6
|
Regioselective Biotransformation of Phloretin Using Streptomyces avermitilis MA4680. BIOTECHNOL BIOPROC E 2020. [DOI: 10.1007/s12257-019-0441-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
7
|
Guengerich FP. Kinetic Modeling of Steady-State Situations in Cytochrome P450 Enzyme Reactions. Drug Metab Dispos 2019; 47:1232-1239. [PMID: 31427434 DOI: 10.1124/dmd.119.088732] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Accepted: 08/14/2019] [Indexed: 12/18/2022] Open
Abstract
In the course of investigations of the kinetics of individual reactions of cytochrome P450 (P450) enzymes, a number of points about the complexity of P450 enzyme kinetics have become apparent. Several of these are of particular relevance to work with P450 enzymes in the course of drug development and lead optimization, particularly with regard to estimating in vitro kinetic parameters and dealing with enzyme inhibitors. Modern simulation modeling has been applied to situations involving issues of preincubation time with moderate strength and strong inhibitors, inhibition by tightly bound ligands that have been identified in P450 enzymes, extensive substrate depletion, P450 reactions with a rate-limiting step after product formation, and the consumption of an inhibitor during a reaction by either a P450 enzyme being monitored or another one in a mixture. The results all follow from first principles, and simulations reveal the extent of their significance in various settings. The order of addition of substrate and inhibitors can change the apparent outcome (inhibition constant, K i), and the effect of the order is more pronounced with a stronger inhibitor. Substrate depletion alters parameters (Michaelis constant, K m) and can generate apparently sigmoidal plots. A rate-limiting step after product formation lowers the apparent K m and distorts K i Consumption of an inhibitor during a reaction affects K i and differs depending on which enzyme is involved. The results are relevant with P450 enzymes and other enzymes as well. SIGNIFICANCE STATEMENT: Kinetic simulations have been used to address several potential problems in enzyme kinetic analysis. Although the simulations done here are general for enzyme reactions, several problems addressed here are particularly relevant to cytochrome P450 reactions encountered in drug development work.
Collapse
Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee
| |
Collapse
|
8
|
Albertolle ME, Peter Guengerich F. The relationships between cytochromes P450 and H 2O 2: Production, reaction, and inhibition. J Inorg Biochem 2018; 186:228-234. [PMID: 29990746 PMCID: PMC6084448 DOI: 10.1016/j.jinorgbio.2018.05.014] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 04/25/2018] [Accepted: 05/23/2018] [Indexed: 12/26/2022]
Abstract
In this review we address the relationship between cytochromes P450 (P450) and H2O2. This association can affect biology in three distinct ways. First, P450s produce H2O2 as a byproduct either during catalysis or when no substrate is present. This reaction, known as uncoupling, releases reactive oxygen species that may have implications in disease. Second, H2O2 is used as an oxygen-donating co-substrate in peroxygenase and peroxidase reactions catalyzed by P450s. This activity has proven to be important mainly in reactions involving prokaryotic P450s, and investigators have harnessed this reaction with the aim of adaptation for industrial use. Third, H2O2-dependent inhibition of human P450s has been studied in our laboratory, demonstrating heme destruction and also the inactivating oxidation of the heme-thiolate ligand to a sulfenic acid (-SOH). This reversible oxidative modification of P450s may have implications in the prevention of uncoupling and may give new insights into the oxidative regulation of these enzymes. Research has elucidated many of the chemical mechanisms involved in the relationship between P450 and H2O2, but the application to biology is difficult to evaluate. Further studies are needed reveal both the harmful and protective natures of reactive oxygen species in an organismal context.
Collapse
Affiliation(s)
- Matthew E Albertolle
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, United States
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, United States.
| |
Collapse
|
9
|
Abstract
Cytochrome P450 (P450, CYP) research provides many opportunities for the application of kinetic isotope effect (KIE) strategies. P450s collectively catalyze oxidations of more substrates than any other group of enzymes, and CH bond cleavage is a major feature in a large fraction of these reactions. The presence of a significant primary deuterium KIE is evidence that hydrogen abstraction is at least partially rate-limiting in the reactions, and this appears to be the case in many P450 reactions. The first report of a KIE in (P450-linked) drug metabolism appeared in 1961 (for morphine N-demethylation), and in a number of cases, it has been possible to modulate the in vivo metabolism or toxicity of chemicals by deuterium substitution. A number of efforts are in progress to utilize deuterium substitution to alter the metabolism of drugs in an advantageous manner.
Collapse
|
10
|
Abstract
The biochemical facets of toxicology have always had a major role in providing insight into mechanisms. Some of the history of the development of this area is summarized, including metabolism, enzymology, and the chemistry of reactive intermediates. Knowledge in these fields has had a major impact in the areas of drug metabolism and safety assessment, which are both critical steps in the development of pharmaceuticals and the rational use of commodity chemicals. The science of toxicology has developed considerably with input from other disciplines and today is poised to emerge as a predictive science with even more dramatic impact. The challenges ahead are considerable but there is renewed excitement in the potential of the field. As in the past, further advances in the field of toxicology will require the input of knowledge from many disciplines.
Collapse
Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
| |
Collapse
|
11
|
Borkar RM, Bhandi MM, Dubey AP, Nandekar PP, Sangamwar AT, Banerjee SK, Srinivas R. Plasma protein binding, pharmacokinetics, tissue distribution and CYP450 biotransformation studies of fidarestat by ultra high performance liquid chromatography–high resolution mass spectrometry. J Pharm Biomed Anal 2015; 102:386-99. [DOI: 10.1016/j.jpba.2014.10.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 10/06/2014] [Accepted: 10/08/2014] [Indexed: 11/16/2022]
|
12
|
Kim D, Cha GS, Nagy LD, Yun CH, Guengerich FP. Kinetic analysis of lauric acid hydroxylation by human cytochrome P450 4A11. Biochemistry 2014; 53:6161-72. [PMID: 25203493 PMCID: PMC4188250 DOI: 10.1021/bi500710e] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Cytochrome P450 (P450) 4A11 is the
only functionally active subfamily
4A P450 in humans. P450 4A11 catalyzes mainly ω-hydroxylation
of fatty acids in liver and kidney; this process is not a major degradative
pathway, but at least one product, 20-hydroxyeicosatetraenoic acid,
has important signaling properties. We studied catalysis by P450 4A11
and the issue of rate-limiting steps using lauric acid ω-hydroxylation,
a prototypic substrate for this enzyme. Some individual reaction steps
were studied using pre-steady-state kinetic approaches. Substrate
and product binding and release were much faster than overall rates
of catalysis. Reduction of ferric P450 4A11 (to ferrous) was rapid
and not rate-limiting. Deuterium kinetic isotope effect (KIE) experiments
yielded low but reproducible values (1.2–2) for 12-hydroxylation
with 12-2H-substituted lauric acid. However, considerable
“metabolic switching” to 11-hydroxylation was observed
with [12-2H3]lauric acid. Analysis of switching
results [Jones, J. P., et al. (1986) J. Am. Chem. Soc.108, 7074–7078] and the use of tritium KIE
analysis with [12-3H]lauric acid [Northrop, D. B. (1987) Methods Enzymol.87, 607–625] both
indicated a high intrinsic KIE (>10). Cytochrome b5 (b5) stimulated steady-state
lauric acid ω-hydroxylation ∼2-fold; the apoprotein was
ineffective, indicating that electron transfer is involved in the b5 enhancement. The rate of b5 reoxidation was increased in the presence of ferrous
P450 mixed with O2. Collectively, the results indicate
that both the transfer of an electron to the ferrous·O2 complex and C–H bond-breaking limit the rate of P450 4A11
ω-oxidation.
Collapse
Affiliation(s)
- Donghak Kim
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
| | | | | | | | | |
Collapse
|
13
|
Wang X, Li J, Dong G, Yue J. The endogenous substrates of brain CYP2D. Eur J Pharmacol 2013; 724:211-8. [PMID: 24374199 DOI: 10.1016/j.ejphar.2013.12.025] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 12/17/2013] [Accepted: 12/17/2013] [Indexed: 12/19/2022]
Abstract
CYP2D6, one of the major cytochrome P450 isoforms present in the human brain, is associated with the incidence and prevalence of central nervous system (CNS) diseases. Human CYP2D6 and rat CYP2D are involved in the metabolism of various neurotransmitters and neurosteroids. Brain CYP2D can be regulated by endogenous steroids, including sex hormones. The alteration of CYP2D-mediated metabolism induced by endogenous steroids may cause changes in sensitivity to environmental and industrial toxins and carcinogens as well as physiological and pathophysiological processes controlled by biologically active compounds. This review summarizes the current knowledge regarding the distribution, endogenous substrates, and regulation of brain CYP2D.
Collapse
Affiliation(s)
- Xiaoshuang Wang
- Department of Pharmacology, School of Medical Sciences, Wuhan University, No. 185 East Lake Road, Wuhan 430071, China; Department of Pharmacy, Wuhan Puren Hospital, Wuhan 430081, China
| | - Jie Li
- Department of Pharmacology, School of Medical Sciences, Wuhan University, No. 185 East Lake Road, Wuhan 430071, China
| | - Guicheng Dong
- Baotou Teachers' College, Inner Mongolia University of Science & Technology, Baotou 014030, China
| | - Jiang Yue
- Department of Pharmacology, School of Medical Sciences, Wuhan University, No. 185 East Lake Road, Wuhan 430071, China.
| |
Collapse
|
14
|
Guengerich FP. Kinetic deuterium isotope effects in cytochrome P450 oxidation reactions. J Labelled Comp Radiopharm 2013; 56:428-31. [PMID: 24285515 PMCID: PMC4861049 DOI: 10.1002/jlcr.3031] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/08/2013] [Accepted: 01/14/2013] [Indexed: 11/09/2022]
Abstract
Cytochrome P450 (P450) enzymes account for ~75% of the metabolism of drugs. Most of the reactions catalyzed by P450s are mixed-function oxidations, and a C-H bond is (usually) broken. The rate-limiting nature of this step can be analyzed using the kinetic isotope effect (KIE) approach. The most relevant type of KIE is one termed intermolecular non-competitive, indicative of rate-limiting C-H bond breaking. A plot of KIE versus kcat for several P450s showed a correlation coefficient (r(2) ) of 0.62. Deuterium substitution has been considered as a potential means of slowing drug metabolism or redirecting sites of metabolism in some cases, and several general points can be made regarding the potential for application of deuterium in drug design/development based on what is known about P450 KIEs.
Collapse
Affiliation(s)
- F. Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| |
Collapse
|
15
|
Yoshimoto FK, Zhou Y, Peng HM, Stidd D, Yoshimoto JA, Sharma KK, Matthew S, Auchus RJ. Minor activities and transition state properties of the human steroid hydroxylases cytochromes P450c17 and P450c21, from reactions observed with deuterium-labeled substrates. Biochemistry 2012; 51:7064-77. [PMID: 22873692 DOI: 10.1021/bi300895w] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The steroid hydroxylases CYP17A1 (P450c17, 17-hydroxylase/17,20-lyase) and CYP21A2 (P450c21, 21-hydroxylase) catalyze progesterone hydroxylation at one or more sites within a 2 Å radius. We probed their hydrogen atom abstraction mechanisms and regiochemical plasticity with deuterium-labeled substrates: 17-[(2)H]-pregnenolone; 17-[(2)H]-, 16α-[(2)H]-, 21,21,21-[(2)H(3)]-, and 21-[(2)H]-progesterone; and 21,21,21-[(2)H(3)]-17-hydroxyprogesterone. Product distribution and formation rates with recombinant human P450-oxidoreductase and wild-type human CYP17A1 or mutation A105L (reduced progesterone 16α-hydroxylation) and wild-type human CYP21A2 or mutation V359A (substantial progesterone 16α-hydroxylation) were used to calculate intramolecular and intermolecular kinetic isotope effects (KIEs). The intramolecular KIEs for CYP17A1 and mutation A105L were 4.1 and 3.8, respectively, at H-17 and 2.9 and 5.1, respectively, at H-16α. Mutation A105L 21-hydroxylates progesterone (5% of products), and wild-type CYP17A1 also catalyzes a trace of 21-hydroxylation, which increases with 16α-[(2)H]- and 17-[(2)H]-progesterone. The intramolecular KIEs with CYP21A2 mutation V359A and progesterone were 6.2 and 3.8 at H-21 and H-16α, respectively. Wild-type CYP21A2 also forms a trace of 16α-hydroxyprogesterone, which increased with 21,21,21-[(2)H(3)]-progesterone substrate. Competitive intermolecular KIEs paralleled the intramolecular KIE values, with (D)V values of 1.4-5.1 and (D)V/K values of 1.8-5.1 for these reactions. CYP17A1 and CYP21A2 mutation V359A both 16α-hydroxylate 16α-[(2)H]-progesterone with 33-44% deuterium retention, indicating stereochemical inversion. We conclude that human CYP17A1 has progesterone 21-hydroxylase activity and human CYP21A2 has progesterone 16α-hydroxylase activity, both of which are enhanced with deuterated substrates. The transition states for C-H bond cleavage in these hydroxylation reactions are either significantly nonlinear and/or asymmetric, and C-H bond breakage is partially rate-limiting for all reactions.
Collapse
Affiliation(s)
- Francis K Yoshimoto
- Division of Endocrinology & Metabolism, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Jang HH, Kim SY, Kang JY, Park SH, Ryu SH, Ahn T, Yun CH. Increase of human CYP1B1 activities by acidic phospholipids and kinetic deuterium isotope effects on CYP1B1 substrate oxidation. J Biochem 2012; 152:433-42. [PMID: 22888116 DOI: 10.1093/jb/mvs087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The effect of phospholipids on the kinetic parameters of three substrates, 7-ethoxy-4 -(trifluoromethyl)coumarin (7-EFC), 7-ethoxycoumarin (7-EC) and 17β-estradiol (E(2)), of human CYP1B1 was studied. In general, anionic phospholipids, phosphatidic acid and cardiolipin increased catalytic efficiency by increasing k(cat) values or decreasing K(m) values. The advantages of using the 7-EFC as a substrate over 7-EC and E(2) include high k(cat), low K(m) and high catalytic efficiency. Spectral binding titrations indicated that the binding affinity of 7-EFC to CYP1B1 in the presence or absence of phospholipids is higher than that of 7-EC or E(2). Furthermore, phosphatidylcholine increased the binding affinity of the substrates to the CYP1B1. High non-competitive intermolecular kinetic deuterium isotope effects (values 5.4-12) were observed for O-deethylation of 7-EFC and 7-EC with deuterium substitution at the ethoxy group, indicating that the C-H bond-breaking step makes a major contribution to the rate of these CYP1B1-catalyzed reactions. However, the intermolecular kinetic deuterium isotope effect is ~2 for the E(2) 4-hydroxylation reaction, indicating that the C-H bond-breaking step contributes only partially to the rate of this CYP1B1-catalyzed reaction. These results indicate that the reaction mechanism of CYP1B1-catalyzed reactions is distinct for each substrate.
Collapse
Affiliation(s)
- Hyun-Hee Jang
- School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
17
|
Berka K, Anzenbacherová E, Hendrychová T, Lange R, Mašek V, Anzenbacher P, Otyepka M. Binding of quinidine radically increases the stability and decreases the flexibility of the cytochrome P450 2D6 active site. J Inorg Biochem 2012; 110:46-50. [DOI: 10.1016/j.jinorgbio.2012.02.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Revised: 01/13/2012] [Accepted: 02/15/2012] [Indexed: 11/25/2022]
|
18
|
Shamovsky I, Ripa L, Börjesson L, Mee C, Nordén B, Hansen P, Hasselgren C, O’Donovan M, Sjö P. Explanation for Main Features of Structure–Genotoxicity Relationships of Aromatic Amines by Theoretical Studies of Their Activation Pathways in CYP1A2. J Am Chem Soc 2011; 133:16168-85. [DOI: 10.1021/ja206427u] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Igor Shamovsky
- Department of Medicinal Chemistry, R&I iMed, AstraZeneca R&D, Pepparedsleden 1, S-431 83 Mölndal, Sweden
| | - Lena Ripa
- Department of Medicinal Chemistry, R&I iMed, AstraZeneca R&D, Pepparedsleden 1, S-431 83 Mölndal, Sweden
| | - Lena Börjesson
- Department of Medicinal Chemistry, R&I iMed, AstraZeneca R&D, Pepparedsleden 1, S-431 83 Mölndal, Sweden
| | - Christine Mee
- Genetic Toxicology, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire SK10 4TG, United Kingdom
| | - Bo Nordén
- Department of Medicinal Chemistry, R&I iMed, AstraZeneca R&D, Pepparedsleden 1, S-431 83 Mölndal, Sweden
| | - Peter Hansen
- Department of Medicinal Chemistry, R&I iMed, AstraZeneca R&D, Pepparedsleden 1, S-431 83 Mölndal, Sweden
| | | | - Mike O’Donovan
- Genetic Toxicology, AstraZeneca R&D, Alderley Park, Macclesfield, Cheshire SK10 4TG, United Kingdom
| | - Peter Sjö
- Department of Medicinal Chemistry, R&I iMed, AstraZeneca R&D, Pepparedsleden 1, S-431 83 Mölndal, Sweden
| |
Collapse
|
19
|
Li Y, Ren G, Wang YX, Kong WJ, Yang P, Wang YM, Li YH, Yi H, Li ZR, Song DQ, Jiang JD. Bioactivities of berberine metabolites after transformation through CYP450 isoenzymes. J Transl Med 2011; 9:62. [PMID: 21569619 PMCID: PMC3103436 DOI: 10.1186/1479-5876-9-62] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2011] [Accepted: 05/15/2011] [Indexed: 12/02/2022] Open
Abstract
Background Berberine (BBR) is a drug with multiple effects on cellular energy metabolism. The present study explored answers to the question of which CYP450 (Cytochrome P450) isoenzymes execute the phase-I transformation for BBR, and what are the bioactivities of its metabolites on energy pathways. Methods BBR metabolites were detected using LC-MS/MS. Computer-assistant docking technology as well as bioassays with recombinant CYP450s were employed to identify CYP450 isoenzymes responsible for BBR phase-I transformation. Bioactivities of BBR metabolites in liver cells were examined with real time RT-PCR and kinase phosphorylation assay. Results In rat experiments, 4 major metabolites of BBR, berberrubine (M1), thalifendine (M2), demethyleneberberine (M3) and jatrorrhizine (M4) were identified in rat's livers using LC-MS/MS (liquid chromatography-tandem mass spectrometry). In the cell-free transformation reactions, M2 and M3 were detectable after incubating BBR with rCYP450s or human liver microsomes; however, M1 and M4 were below detective level. CYP2D6 and CYP1A2 played a major role in transforming BBR into M2; CYP2D6, CYP1A2 and CYP3A4 were for M3 production. The hepatocyte culture showed that BBR was active in enhancing the expression of insulin receptor (InsR) and low-density-lipoprotein receptor (LDLR) mRNA, as well as in activating AMP-activated protein kinase (AMPK). BBR's metabolites, M1-M4, remained to be active in up-regulating InsR expression with a potency reduced by 50-70%; LDLR mRNA was increased only by M1 or M2 (but not M3 and M4) with an activity level 35% or 26% of that of BBR, respectively. Similarly, AMPK-α phosphorylation was enhanced by M1 and M2 only, with a degree less than that of BBR. Conclusions Four major BBR metabolites (M1-M4) were identified after phase-I transformation in rat liver. Cell-free reactions showed that CYP2D6, CYP1A2 and CYP3A4 seemed to be the dominant CYP450 isoenzymes transforming BBR into its metabolites M2 and M3. BBR's metabolites remained to be active on BBR's targets (InsR, LDLR, and AMPK) but with reduced potency.
Collapse
Affiliation(s)
- Yi Li
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Schyman P, Lai W, Chen H, Wang Y, Shaik S. The directive of the protein: how does cytochrome P450 select the mechanism of dopamine formation? J Am Chem Soc 2011; 133:7977-84. [PMID: 21539368 DOI: 10.1021/ja201665x] [Citation(s) in RCA: 200] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dopamine can be generated from tyramine via arene hydroxylation catalyzed by a cytochrome P450 enzyme (CYP2D6). Our quantum mechanical/molecular mechanical (QM/MM) results reveal the decisive impact of the protein in selecting the 'best' reaction mechanism. Instead of the traditional Meisenheimer-complex mechanism, the study reveals a mechanism involving an initial hydrogen atom transfer from the phenolic hydroxyl group of the tyramine to the iron-oxo of the compound I (Cpd I), followed by a ring-π radical rebound that eventually leads to dopamine by keto-enol rearrangement. This mechanism is not viable in the gas phase since the O-H bond activation by Cpd I is endothermic and the process does not form a stable intermediate. By contrast, the in-protein reaction has a low barrier and is exothermic. It is shown that the local electric field of the protein environment serves as a template that stabilizes the intermediate of the H-abstraction step and thereby mediates the catalysis of dopamine formation at a lower energy cost. Furthermore, it is shown that external electric fields can either catalyze or inhibit the process depending on their directionality.
Collapse
Affiliation(s)
- Patric Schyman
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | | | | | | | | |
Collapse
|
21
|
Bach RD. The rate-limiting step in P450 hydroxylation of hydrocarbons a direct comparison of the "somersault" versus the "consensus" mechanism involving compound I. J Phys Chem A 2010; 114:9319-32. [PMID: 20690650 DOI: 10.1021/jp1045518] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Model theoretical quantum mechanical (QM) calculations are described for the P-450 hydroxylation of methane, isobutane, and camphor that compare the concerted somersault H-abstraction mechanism with the oxidation step involving Cpd I. Special emphasis has been placed on maintaining a balanced basis set in the oxidation step. QM calculations, employing the 6-311+G(d,p) basis set on the Fe atom and all of the key surrounding atoms involved in the C-H abstraction step, reaffirm a mechanism involving rearrangement of the iron hydroperoxide group (FeO-OH --> FeO...HO(*)) in concert with hydrogen abstraction from the C-H bond of the substrate by the incipient bound hydroxyl radical HO(*). The barrier for the somersault rearrangement of model Cpd 0 (FeO-OH) is calculated to be 21.4 kcal/mol in the absence of substrate. The overall activation energy for the oxidation of camphor involving the somersault motion of the FeO-OH group of P450 model porphyrin iron(III) hydroperoxide [Por(SH)Fe(III)-OOH(-)] --> [Por(SH)Fe(III)-O....HO(-)] in concert with hydrogen abstraction is DeltaE(++) = 12.4 kcal/mol. The corresponding abstraction of the hydrogen atom from the C-H bond of camphor by Cpd I has an activation barrier of 17.6 kcal/mol. Arguments are presented that the somersault rearrangement is induced by steric compression at the active site. Kinetic isotope effect data are discussed that provides compelling evidence for a rate-limiting step involving C-H bond cleavage.
Collapse
Affiliation(s)
- Robert D Bach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA.
| |
Collapse
|
22
|
Shinkyo R, Guengerich FP. Cytochrome P450 7A1 cholesterol 7alpha-hydroxylation: individual reaction steps in the catalytic cycle and rate-limiting ferric iron reduction. J Biol Chem 2010; 286:4632-43. [PMID: 21147774 DOI: 10.1074/jbc.m110.193409] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytochrome P450 (P450) 7A1 is well known as the cholesterol 7α-hydroxylase, the first enzyme involved in bile acid synthesis from cholesterol. The human enzyme has been reported to have the highest catalytic activity of any mammalian P450. Analyses of individual steps of cholesterol 7α-hydroxylation reaction revealed several characteristics of this reaction: (i) two-step binding of cholesterol to ferric P450, with an apparent K(d) of 0.51 μM, (ii) a rapid reduction rate in the presence of cholesterol (∼10 s(-1) for the fast phase), (iii) rapid formation of a ferrous P450-cholesterol-O(2) complex (29 s(-1)), (iv) the lack of a non-competitive kinetic deuterium isotope effect, (v) the lack of a kinetic burst, and (vi) the lack of a deuterium isotope effect when the reaction was initiated with the ferrous P450-cholesterol complex. A minimum kinetic model was developed and is consistent with all of the observed phenomena and the rates of cholesterol 7α-hydroxylation and H(2)O and H(2)O(2) formation. The results indicate that the first electron transfer step, although rapid, becomes rate-limiting in the overall P450 7A1 reaction. This is a different phenomenon compared with other P450s that have much lower rates of catalysis, attributed to the much more efficient substrate oxidation steps in this reaction.
Collapse
Affiliation(s)
- Raku Shinkyo
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
| | | |
Collapse
|
23
|
Schyman P, Usharani D, Wang Y, Shaik S. Brain chemistry: how does P450 catalyze the O-demethylation reaction of 5-methoxytryptamine to yield serotonin? J Phys Chem B 2010; 114:7078-89. [PMID: 20405876 DOI: 10.1021/jp1008994] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Density functional theory has been applied to elucidate the mechanism of the O-demethylation reaction that generates serotonin from 5-methoxytryptamine (5-MT); a process that is efficiently catalyzed by P450 CYP2D6. Two substrates, the neutral 5-MT and the protonated 5-MTH(+), were used to probe the reactivity of CYP2D6 compound I. Notably, the H-abstraction process is found to be slightly more facile for 5-MT. However, our DFT augmented by docking results show that the amino acid Glu216 in the active site holds the NH(3)(+) tail of the 5-MTH(+) substrate in an upright conformation and thereby controls the regioselectivity of the bond activation. Thus, the substrate protonation serves an important function in maximizing the yield of serotonin. This finding is in accord with experimental conclusions that 5-MTH(+) serves as the substrate for the CYP2D6 enzyme. The study further shows that the H-abstraction follows two-state reactivity (TSR), whereas the rebound path may involve more states due to the appearance of both Fe(IV) and Fe(III) electromers during the reaction of 5-MTH(+).
Collapse
Affiliation(s)
- Patric Schyman
- Institute of Chemistry and The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91940 Jerusalem, Israel
| | | | | | | |
Collapse
|
24
|
Affiliation(s)
- Paul R. Ortiz de Montellano
- Department of Pharmaceutical Chemistry, University of California, 600 16 Street, San Francisco, California 94158-2517
| |
Collapse
|
25
|
Shaik S, Cohen S, Wang Y, Chen H, Kumar D, Thiel W. P450 Enzymes: Their Structure, Reactivity, and Selectivity—Modeled by QM/MM Calculations. Chem Rev 2009; 110:949-1017. [DOI: 10.1021/cr900121s] [Citation(s) in RCA: 791] [Impact Index Per Article: 52.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sason Shaik
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Shimrit Cohen
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Yong Wang
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Hui Chen
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Devesh Kumar
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Walter Thiel
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| |
Collapse
|
26
|
Grobe N, Zhang B, Fisinger U, Kutchan TM, Zenk MH, Guengerich FP. Mammalian cytochrome P450 enzymes catalyze the phenol-coupling step in endogenous morphine biosynthesis. J Biol Chem 2009; 284:24425-31. [PMID: 19561069 PMCID: PMC2782035 DOI: 10.1074/jbc.m109.011320] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 05/27/2009] [Indexed: 11/06/2022] Open
Abstract
A cytochrome P450 (P450) enzyme in porcine liver that catalyzed the phenol-coupling reaction of the substrate (R)-reticuline to salutaridine was previously purified to homogeneity (Amann, T., Roos, P. H., Huh, H., and Zenk, M. H. (1995) Heterocycles 40, 425-440). This reaction was found to be catalyzed by human P450s 2D6 and 3A4 in the presence of (R)-reticuline and NADPH to yield not a single product, but rather (-)-isoboldine, (-)-corytuberine, (+)-pallidine, and salutaridine, the para-ortho coupled established precursor of morphine in the poppy plant and most likely also in mammals. (S)-Reticuline, a substrate of both P450 enzymes, yielded the phenol-coupled alkaloids (+)-isoboldine, (+)-corytuberine, (-)-pallidine, and sinoacutine; none of these serve as a morphine precursor. Catalytic efficiencies were similar for P450 2D6 and P450 3A4 in the presence of cytochrome b(5) with (R)-reticuline as substrate. The mechanism of phenol coupling is not yet established; however, we favor a single cycle of iron oxidation to yield salutaridine and the three other alkaloids from (R)-reticuline. The total yield of salutaridine formed can supply the 10 nm concentration of morphine found in human neuroblastoma cell cultures and in brain tissues of mice.
Collapse
Affiliation(s)
- Nadja Grobe
- From the Donald Danforth Plant Science Center, St. Louis, Missouri 63132
| | - Baichen Zhang
- From the Donald Danforth Plant Science Center, St. Louis, Missouri 63132
| | - Ursula Fisinger
- the Lehrstuhl für Pharmazeutische Biologie, Universität München, Karlstrasse 29, 80333 München, Germany, and
| | - Toni M. Kutchan
- From the Donald Danforth Plant Science Center, St. Louis, Missouri 63132
| | - Meinhart H. Zenk
- From the Donald Danforth Plant Science Center, St. Louis, Missouri 63132
| | - F. Peter Guengerich
- the Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146
| |
Collapse
|
27
|
Teksin ZS, Lee IJ, Nemieboka NN, Othman AA, Upreti VV, Hassan HE, Syed SS, Prisinzano TE, Eddington ND. Evaluation of the transport, in vitro metabolism and pharmacokinetics of Salvinorin A, a potent hallucinogen. Eur J Pharm Biopharm 2009; 72:471-7. [PMID: 19462483 DOI: 10.1016/j.ejpb.2009.01.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Salvinorin A is an unregulated potent hallucinogen isolated from the leaves of Salvia divinorum. It is the only known non-nitrogenous kappa-opioid selective agonist, and rivals synthetic lysergic acid diethylamide (LSD) in potency. The objective of this study was to characterize the in vitro transport, in vitro metabolism, and pharmacokinetic properties of Salvinorin A. The transport characteristics of Salvinorin A were assessed using MDCK-MDR1 cell monolayers. The P-glycoprotein (P-gp) affinity status was assessed by the P-gp ATPase assay. In vitro metabolism studies were performed with various specific human CYP450 isoforms and UGT2B7 to assess the metabolic characteristics of Salvinorin A. Cohorts (n = 3) of male Sprague Dawley rats were used to evaluate the pharmacokinetics and brain distribution of Salvinorin A (10 mg/kg, intraperitoneal (i.p.) over a 240-min period. A validated UV-HPLC and LC/MS/MS method was used to quantify the hallucinogen concentrations obtained from the in vitro and in vivo studies, respectively. Salvinorin A displayed a high secretory transport in the MDCK-MDR1 cells (4.07 +/- 1.34 x 10(-)5 cm/s). Salvinorin A also stimulated the P-gp ATPase activity in a concentration (5 and 10 microM)-dependent manner, suggesting that it may be a substrate of (P-gp). A significant decrease in Salvinorin A concentration ranging from 14.7 +/- 0.80% to 31.1 +/- 1.20% was observed after incubation with CYP2D6, CYP1A1, CYP2C18, and CYP2E1, respectively. A significant decrease was also observed after incubation with UGT2B7. These results suggest that Salvinorin A maybe a substrate of UGT2B7, CYP2D6, CYP1A1, CYP2E1, and CYP2C18. The in vivo pharmacokinetic study showed a relatively fast elimination with a half-life (t1/2) of 75 min and a clearance (Cl/F) of 26 L/h/kg. The distribution was extensive (Vd of 47.1 L/kg); however, the brain to plasma ratio was 0.050. Accordingly, the brain half-life was relatively short, 36 min. Salvinorin A is rapidly eliminated after i.p. dosing, in accordance with its fast onset and short duration of action. Further, it appears to be a substrate for various oxidative enzymes and multi-drug resistant protein, P-gp.
Collapse
Affiliation(s)
- Zeynep S Teksin
- Department of Pharmaceutical Sciences, University of Maryland, Baltimore, MD 21201, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
|
29
|
Francis K, Gadda G. Inflated Kinetic Isotope Effects in the Branched Mechanism of Neurospora crassa 2-Nitropropane Dioxygenase. Biochemistry 2009; 48:2403-10. [DOI: 10.1021/bi802238j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kevin Francis
- Departments of Chemistry and Biology and The Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30302-4098
| | - Giovanni Gadda
- Departments of Chemistry and Biology and The Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30302-4098
| |
Collapse
|
30
|
Tzeng RF, Liu SI, Wu LSH, Chen ST, Yu YH, Li PC, Chern SR, Lee PY, Lan TH, Loh EW. High proportion of single CYP2D6 gene deletion in Chinese attention-deficit-hyperactivity disorder children and its risk in oppositional defiant disorder. Psychiatry Clin Neurosci 2008; 62:749. [PMID: 19068017 DOI: 10.1111/j.1440-1819.2008.01885.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
31
|
Stefano GB, Cadet P, Kream RM, Zhu W. The presence of endogenous morphine signaling in animals. Neurochem Res 2008; 33:1933-9. [PMID: 18777209 DOI: 10.1007/s11064-008-9674-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 03/13/2008] [Indexed: 11/28/2022]
Abstract
Recent empirical findings have contributed valuable mechanistic information in support of a regulated de novo biosynthetic pathway for chemically authentic morphine and related morphinan alkaloids within animal cells. Importantly, we and others have established that endogenously expressed morphine represents a key regulatory molecule effecting local circuit autocrine/paracrine cellular signaling via a novel mu(3) opiate receptor coupled to constitutive nitric oxide production and release. The present report provides an integrated review of the biochemical, pharmacological, and molecular demonstration of mu(3) opiate receptors in historical linkage to the elucidation of mechanisms of endogenous morphine production by animal cells and organ systems. Ongoing research in this exciting area provides a rare window of opportunity to firmly establish essential biochemical linkages between dopamine, a morphine precursor, and animal biosynthetic pathways involved in morphine biosynthesis that have been conserved throughout evolution.
Collapse
Affiliation(s)
- George B Stefano
- Neuroscience Research Institute, State University of New York-College at Old Westbury, P.O. Box 210, Old Westbury, NY 11568, USA.
| | | | | | | |
Collapse
|
32
|
Stefano GB, Kream RM, Mantione KJ, Sheehan M, Cadet P, Zhu W, Bilfinger TV, Esch T. Endogenous morphine/nitric oxide-coupled regulation of cellular physiology and gene expression: implications for cancer biology. Semin Cancer Biol 2007; 18:199-210. [PMID: 18203618 DOI: 10.1016/j.semcancer.2007.12.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Accepted: 12/05/2007] [Indexed: 12/19/2022]
Abstract
Cancer is a simplistic, yet complicated, process that promotes uncontrolled growth. In this regard, this unconstrained proliferation may represent primitive phenomena whereby cellular regulation is suspended or compromised. Given the new empirical evidence for a morphinergic presence and its profound modulatory actions on several cellular processes it is not an overstatement to hypothesize that morphine may represent a key chemical messenger in the process of modulating proliferation of diverse cells. This has been recently demonstrated by the finding of a novel opiate-alkaloid selective receptor subtype in human multilineage progenitor cells (MLPC). Adding to the significance of morphinergic signaling are the findings of its presence in plant, invertebrate and vertebrate cells, which also have been shown to synthesize this messenger as well. Interestingly, we and others have shown that some cancerous tissues contain morphine. Furthermore, in medullary histolytic reticulosis, which is exemplified by cells having hyperactivity, the mu3 (mu3) opiate select receptor was not present. Thus, it would appear that morphinergic signaling has inserted itself in many processes taking a long time to evolve, including those regulating the proliferation of cells across diverse phyla.
Collapse
Affiliation(s)
- George B Stefano
- Neuroscience Research Institute, State University of New York - SUNY College at Old Westbury, P.O. Box 210, Old Westbury, NY 11568, USA.
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Insights into drug metabolism by cytochromes P450 from modelling studies of CYP2D6-drug interactions. Br J Pharmacol 2007; 153 Suppl 1:S82-9. [PMID: 18026129 DOI: 10.1038/sj.bjp.0707570] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The cytochromes P450 (CYPs) comprise a vast superfamily of enzymes found in virtually all life forms. In mammals, xenobiotic metabolizing CYPs provide crucial protection from the effects of exposure to a wide variety of chemicals, including environmental toxins and therapeutic drugs. Ideally, the information on the possible metabolism by CYPs required during drug development would be obtained from crystal structures of all the CYPs of interest. For some years only crystal structures of distantly related bacterial CYPs were available and homology modelling techniques were used to bridge the gap and produce structural models of human CYPs, and thereby obtain useful functional information. A significant step forward in the reliability of these models came seven years ago with the first crystal structure of a mammalian CYP, rabbit CYP2C5, followed by the structures of six human enzymes, CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6 and CYP3A4, and a second rabbit enzyme, CYP2B4. In this review we describe as a case study the evolution of a CYP2D6 model, leading to the validation of the model as an in silico tool for predicting binding and metabolism. This work has led directly to the successful design of CYP2D6 mutants with novel activity-including creating a testosterone hydroxylase, converting quinidine from inhibitor to substrate, creating a diclofenac hydroxylase and creating a dextromethorphan O-demethylase. Our modelling-derived hypothesis-driven integrated interdisciplinary studies have given key insight into the molecular determinants of CYP2D6 and other important drug metabolizing enzymes.
Collapse
|
34
|
Porter SEG, Keithley RB, Rutan SC. Development of an in vitro incubation procedure for screening of CYP2D6 intrinsic clearance. J Chromatogr B Analyt Technol Biomed Life Sci 2007; 850:74-82. [PMID: 17127110 DOI: 10.1016/j.jchromb.2006.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Revised: 10/30/2006] [Accepted: 11/03/2006] [Indexed: 11/30/2022]
Abstract
The in vitro intrinsic clearances (CL(int)) for the metabolism of p-methoxymethamphetamine (PMMA) and fluoxetine by the CYP2D6 enzyme were calculated using a steady-state (SS) approach and a new general enzyme (GE) method, which measures the formation of product and the depletion of substrate as a function of time. For PMMA, the SS experiment resulted in a CL(int) of 2.7+/-0.2 microL pmol 2D6(-1)min(-1) and the GE experiment resulted in a CL(int) of 3.0+/-0.6 microL pmol 2D6(-1)min(-1). For fluoxetine, the SS experiment resulted in a CL(int) of 0.33+/-0.17 microL pmol 2D6(-1)min(-1) and the GE experiment resulted in a CL(int) of 0.188+/-0.013 microL pmol 2D6(-1)min(-1). We used two kinetic modeling techniques that can accommodate atypical kinetic models. We also show that the addition of fluoxetine results in a 10-fold decrease in the observed intrinsic clearance of PMMA, confirming that fluoxetine is a potent inhibitor of the liver enzyme CYP2D6.
Collapse
Affiliation(s)
- Sarah E G Porter
- Virginia Commonwealth University, Department of Chemistry, 1001 W. Main Street, Box 842006, Richmond, VA 23284-2006, USA
| | | | | |
Collapse
|
35
|
McLaughlin LA, Paine MJI, Kemp CA, Maréchal JD, Flanagan JU, Ward CJ, Sutcliffe MJ, Roberts GCK, Wolf CR. Why Is Quinidine an Inhibitor of Cytochrome P450 2D6? J Biol Chem 2005; 280:38617-24. [PMID: 16162505 DOI: 10.1074/jbc.m505974200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have previously shown that Phe(120), Glu(216), and Asp(301) in the active site of cytochrome P450 2D6 (CYP2D6) play a key role in substrate recognition by this important drug-metabolizing enzyme (Paine, M. J., McLaughlin, L. A., Flanagan, J. U., Kemp, C. A., Sutcliffe, M. J., Roberts, G. C., and Wolf, C. R. (2003) J. Biol. Chem. 278, 4021-4027 and Flanagan, J. U., Maréchal, J.-D., Ward, R., Kemp, C. A., McLaughlin, L. A., Sutcliffe, M. J., Roberts, G. C., Paine, M. J., and Wolf, C. R. (2004) Biochem. J. 380, 353-360). We have now examined the effect of mutations of these residues on interactions of the enzyme with the prototypical CYP2D6 inhibitor, quinidine. Abolition of the negative charge at either or both residues 216 and 301 decreased quinidine inhibition of bufuralol 1'-hydroxylation and dextromethorphan O-demethylation by at least 100-fold. The apparent dissociation constants (K(d)) for quinidine binding to the wild-type enzyme and the E216D and D301E mutants were 0.25-0.50 microm. The amide substitution of Glu(216) or Asp(301) resulted in 30-64-fold increases in the K(d) for quinidine. The double mutant E216Q/D301Q showed the largest decrease in quinidine affinity, with a K(d) of 65 microm. Alanine substitution of Phe(120), Phe(481),or Phe(483) had only a minor effect on the inhibition of bufuralol 1'-hydroxylation and dextromethorphan O-demethylation and on binding. In contrast to the wild-type enzyme, a number of the mutants studied were found to be able to metabolize quinidine. E216F produced O-demethylated quinidine, and F120A and E216Q/D301Q produced both O-demethylated quinidine and 3-hydroxyquinidine metabolites. Homology modeling and molecular docking were used to predict the modes of quinidine binding to the wild-type and mutant enzymes; these were able to rationalize the experimental observations.
Collapse
Affiliation(s)
- Lesley A McLaughlin
- Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Lussenburg BMA, Keizers PHJ, de Graaf C, Hidestrand M, Ingelman-Sundberg M, Vermeulen NPE, Commandeur JNM. The role of phenylalanine 483 in cytochrome P450 2D6 is strongly substrate dependent. Biochem Pharmacol 2005; 70:1253-61. [PMID: 16135359 DOI: 10.1016/j.bcp.2005.07.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 06/30/2005] [Accepted: 07/01/2005] [Indexed: 11/29/2022]
Abstract
The polymorphic cytochrome P450 2D6 (CYP2D6) is involved in the metabolism of 30% of the drugs currently prescribed, and is thus clinically relevant. Typical CYP2D6 substrates generally contain a basic nitrogen atom and an aromatic moiety adjacent to the site of metabolism. Recently, we demonstrated the importance of active site residue F120 in substrate binding and catalysis in CYP2D6. On the basis of protein homology models, it is claimed that another active site phenylalanine, F483, may also play an important role in the interaction with the aromatic moiety of CYP2D6 substrates. Experimental data to support this hypothesis, however, is not yet available. In fact, in the only study performed, mutation of F483 to isoleucine or tryptophan did not affect the 1'-hydroxylation of bufuralol at all [Smith G, Modi S, Pillai I, Lian LY, Sutcliffe MJ, Pritchard MP, et al., Determinants of the substrate specificity of human cytochrome P-450 CYP2D6: design and construction of a mutant with testosterone hydroxylase activity. Biochem J 1998;331:783-92]. In the present study, the role of F483 in ligand binding and metabolism by CYP2D6 was examined experimentally using site-directed mutagenesis. Replacement of F483 by alanine resulted in a 30-fold lower V(max) for bufuralol 1'-hydroxylation, while the K(m) was hardly affected. The V(max) for 3,4-methylenedioxy-methylamphetamine O-demethylenation on the other hand decreased only two-fold, whereas the effect on the K(m) was much larger. For dextromethorphan, in addition to dextrorphan (O-demethylation) and 3-methoxymorphinan (N-demethylation), two other metabolites were formed that could not be detected for the wild-type. The substrate 7-methoxy-4-(aminomethyl)-coumarin was not metabolised at all by CYP2D6[F483A], a phenomenon that was reported also for CYP2D6[F120A]. The presented data show that next to F120, residue F483 plays a very important role in the metabolism of typical CYP2D6 substrates. The influence of F483 on metabolism was found to be strongly substrate-dependent.
Collapse
Affiliation(s)
- Barbara M A Lussenburg
- LACDR/Division of Molecular Toxicology, Department of Pharmacochemistry, Vrije Universiteit, HV Amsterdam, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
37
|
Krauser JA, Guengerich FP. Cytochrome P450 3A4-catalyzed Testosterone 6β-Hydroxylation Stereochemistry, Kinetic Deuterium Isotope Effects, and Rate-limiting Steps. J Biol Chem 2005; 280:19496-506. [PMID: 15772082 DOI: 10.1074/jbc.m501854200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Testosterone 6beta-hydroxylation is a prototypic reaction of cytochrome P450 (P450) 3A4, the major human P450. Biomimetic reactions produced a variety of testosterone oxidation products with 6beta-hydroxylation being only a minor reaction, indicating that P450 3A4 has considerable control over the course of steroid hydroxylation because 6beta-hydroxylation is not dominant in a thermodynamically controlled oxidation of the substrate. Several isotopically labeled testosterone substrates were prepared and used to probe the catalytic mechanism of P450 3A4: (i) 2,2,4,6,6-(2)H(5); (ii) 6,6-(2)H(2); (iii) 6alpha-(2)H; (iv) 6beta-(2)H; and (v) 6beta-(3)H testosterone. Only the 6beta-hydrogen was removed by P450 3A4 and not the 6alpha, indicating that P450 3A4 abstracts hydrogen and rebounds oxygen only at the beta face. Analysis of the rates of hydroxylation of 6beta-(1)H-, 6beta-(2)H-, and 6beta-(3)H-labeled testosterone and application of the Northrop method yielded an apparent intrinsic kinetic deuterium isotope effect ((D)k) of 15. The deuterium isotope effects on k(cat) and k(cat)/K(m) in non-competitive reactions were only 2-3. Some "switching" to other hydroxylations occurred because of 6beta-(2)H substitution. The high (D)k value is consistent with an initial hydrogen atom abstraction reaction. Attenuation of the high (D)k in the non-competitive experiments implies that C-H bond breaking is not a dominant rate-limiting step. Considerable attenuation of a high (D)k value was also seen with a slower P450 3A4 reaction, the O-dealkylation of 7-benzyloxyquinoline. Thus P450 3A4 is an enzyme with regioselective flexibility but also considerable regioselectivity and stereoselectivity in product formation, not necessarily dominated by the ease of C-H bond breaking.
Collapse
Affiliation(s)
- Joel A Krauser
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
| | | |
Collapse
|
38
|
Yun CH, Kim KH, Calcutt MW, Guengerich FP. Kinetic analysis of oxidation of coumarins by human cytochrome P450 2A6. J Biol Chem 2005; 280:12279-91. [PMID: 15665333 DOI: 10.1074/jbc.m411019200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human cytochrome P450 (P450) 2A6 catalyzes 7-hydroxylation of coumarin, and the reaction rate is enhanced by cytochrome b5 (b5). 7-Alkoxycoumarins were O-dealkylated and also hydroxylated at the 3-position. Binding of coumarin and 7-hydroxycoumarin to ferric and ferrous P450 2A6 are fast reactions (k(on) approximately 10(6) m(-1) s(-1)), and the k(off) rates range from 5.7 to 36 s(-1) (at 23 degrees C). Reduction of ferric P450 2A6 is rapid (7.5 s(-1)) but only in the presence of coumarin. The reaction of the ferrous P450 2A6 substrate complex with O2 is rapid (k > or = 10(6) m(-1) s(-1)), and the putative Fe2+.O2 complex decayed at a rate of approximately 0.3 s(-1) at 23 degrees C. Some 7-hydroxycoumarin was formed during the oxidation of the ferrous enzyme under these conditions, and the yield was enhanced by b5. Kinetic analyses showed that approximately 1/3 of the reduced b5 was rapidly oxidized in the presence of the Fe2+.O2 complex, implying some electron transfer. High intrinsic and competitive and non-competitive intermolecular kinetic deuterium isotope effects (values 6-10) were measured for O-dealkylation of 7-alkoxycoumarins, indicating the effect of C-H bond strength on rates of product formation. These results support a scheme with many rapid reaction steps, including electron transfers, substrate binding and release at multiple stages, and rapid product release even though the substrate is tightly bound in a small active site. The inherent difficulty of chemistry of substrate oxidation and the lack of proclivity toward a linear pathway leading to product formation explain the inefficiency of the enzyme relative to highly efficient bacterial P450s.
Collapse
Affiliation(s)
- Chul-Ho Yun
- Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju 500-757, Republic of Korea
| | | | | | | |
Collapse
|
39
|
Abstract
The cytochrome P450 (P450) field came out of interest in the metabolism of drugs, carcinogens, and steroids, which remain major focal points. Over the years we have come to understand the P450 system components, the multiplicity of P450s, and many aspects of the regulation of the genes and also the catalytic mechanism. Many crystal structures are now becoming available. The significance of P450 in in vivo metabolism is appreciated, particularly in the context of pharmacogenetics. Current scientific issues involve posttranslational modification, gene regulation, component interactions, structures of P450 complexed with ligands, details of high-valent oxygen chemistry, the nature and influence of rate-limiting steps, greater details about some reaction steps, cooperativity, and the relevance of P450 variations to cancer risk. Some emerging research areas involve new methods of analysis of ligand interactions, roles of conformational changes linked to individual reaction steps, functions of orphan P450s, "molecular breeding" of new P450 functions and enhanced activity, and the utilization of P450s in chemical synthesis.
Collapse
Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry, Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
| |
Collapse
|
40
|
Guengerich FP, Krauser JA, Johnson WW. Rate-limiting steps in oxidations catalyzed by rabbit cytochrome P450 1A2. Biochemistry 2004; 43:10775-88. [PMID: 15311939 DOI: 10.1021/bi0491393] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Several issues regarding the rate-limiting nature of individual reaction steps in catalysis by rabbit liver cytochrome P450 (P450) 1A2 were addressed using anisoles and other substrates. Substrate binding is very fast (k > 10(6) M(-1) s(-1)). Product release is not rate-limiting, as shown by the absence of bursts, placing rate-limiting steps at or before product formation. We had previously shown that the first 1-electron reduction step is fast (k > 700 min(-1)), even in the absence of ligand [Guengerich, F. P., and Johnson, W. W. (1997) Biochemistry 36, 14741-147500]. O(2) binding to ferrous P450 is fast (k >/= 10(6) M(-1) s(-1)). The decay of the P450 Fe(2+)-substrate-O(2) complex was slow in the absence of NADPH-P450 reductase, with a first-order rate constant of 14 min(-1) at 25 degrees C. During the decay, product was formed (from the substrate methacetin) in 61% theoretical yield, although this reaction requires electron transfer among P450 molecules and may not be related to normal turnover. Steady-state spectra suggest that one or more iron-oxygen complexes accumulate, representing entities between the Fe(2+)-O(2) complex and putative FeO(3+) entity. Kinetic isotope effect experiments were done with several substrates, mainly anisoles. Apparent intrinsic deuterium isotope effects as high as 15 were measured. In all cases, the C-H bond-breaking step is at least partially rate-limiting. The isotope effects were not strongly attenuated in noncompetitive or competitive experiments, consistent with relatively rapid P450-substrate exchange, except with the active enzyme Fe-O complex. Kinetic simulations with the available data (i) are consistent with the view that C-H bond breaking is a major rate-limiting step, (ii) demonstrate that increasing the rate of this step will affect k(cat), K(m), and kinetic hydrogen isotope effects but will only increase catalytic efficiency to a certain degree, (iii) indicate that increasing ground-state binding can increase catalytic efficiency but not k(cat), and (iv) suggest that nonproductive binding modes and abortive reduction of O(2) are factors that attenuate catalytic efficiency.
Collapse
Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
| | | | | |
Collapse
|
41
|
Zhang H, Gruenke L, Arscott D, Shen A, Kasper C, Harris DL, Glavanovich M, Johnson R, Waskell L. Determination of the rate of reduction of oxyferrous cytochrome P450 2B4 by 5-deazariboflavin adenine dinucleotide T491V cytochrome P450 reductase. Biochemistry 2004; 42:11594-603. [PMID: 14529269 DOI: 10.1021/bi034968u] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The use of 5-deazaFAD T491V cytochrome P450 reductase has made it possible to directly measure the rate of electron transfer to microsomal oxyferrous cytochrome (cyt) P450 2B4. In this reductase the FMN moiety can be reduced to the hydroquinone, FMNH(2), while the 5-deazaFAD moiety remains oxidized [Zhang, H., et al. (2003) Biochemistry 42, 6804-6813]. The rate of electron transfer from 5-deazaFAD cyt P450 reductase to oxyferrous cyt P450 was determined by rapidly mixing the ferrous cyt P450-2-electron-reduced 5-deazaFAD T491V reductase complex with oxygen in the presence of substrate. The 5-deazaFAD T491V reductase which can only donate a single electron reduces the oxyferrous cyt P450 and oxidizes to the air-stable semiquinone, with rate constants of 8.4 and 0.37 s(-1) at 15 degrees C. Surprisingly, oxyferrous cyt P450 turns over more slowly with a rate constant of 0.09 s(-1), which is the rate of catalysis under steady-state conditions at 15 degrees C (k(cat) = 0.08 s(-1)). In contrast, the rate constant for electron transfer from ferrous cyt b(5) to oxyferrous cyt P450 is 10 s(-1) with oxyferrous cyt P450 and cyt b(5) simultaneously undergoing spectral changes. Quantitative analyses by LC-MS/MS revealed that the product, norbenzphetamine, was formed with a coupling efficiency of 52% with cyt b(5) and 32% with 5-deazaFAD T491V reductase. Collectively, these results suggest that during catalysis a relatively stable reduced oxyferrous intermediate of cyt P450 is formed in the presence of cyt P450 reductase but not cyt b(5) and that the rate-limiting step in catalysis follows introduction of the second electron.
Collapse
Affiliation(s)
- Haoming Zhang
- University of Michigan and VA Medical Research Center, 2215 Fuller Road, Ann Arbor, Michigan 48105, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Park JY, Harris D. Construction and assessment of models of CYP2E1: predictions of metabolism from docking, molecular dynamics, and density functional theoretical calculations. J Med Chem 2003; 46:1645-60. [PMID: 12699383 DOI: 10.1021/jm020538a] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
3D models of CYP2E1 were constructed for the purpose of structure-based prediction of 2E1 metabolism of diverse substrates based on configuration sampling of ligand-atom-oxyferryl center distances and quantum chemical criteria. Models were constructed on the basis of sequence alignments of 2E1 with templates of known structure, including rabbit CYP2C5 (3LVdH) and bacterial CYP450s. Following geometric and energetic assessments, the utility of the model was tested in structure-based predictions of metabolism. Autodock was used to dock chlorzoxazone, p-nitrophenol, N-nitrosodimethylamine, acetominophen, caffeine, theophylline, and methoxyflurane into the model CYP2E1 employing a model oxyferryl heme with charges based on density functional theoretical parametrization. In all cases, the lowest energy bound docked configurations corresponded to ones with the substrate intimately associated with the oxyferryl center. Configurations among the lowest energy docked forms of each of the ligands had orientations relative to the oxyferryl center consistent with the experimentally observed metabolites. Docking of long-chain dialkylnitrosoamines revealed no heme binding site bound configurations, in agreement with the negligible metabolism of these ligands. The lowest energy docked configurations of chlorzoxazone, p-nitrophenol, and N-nitrosodimethylamine, high-affinity substrates of 2E1, were used to initiate 300 ps molecular dynamics (MD) trajectories. The MD-sampled ligand-oxyferryl heme reactant configurations were in good accord with density functional theoretical (DFT) optimized oxyferryl-heme-ligand geometries. Analysis of the MD-sampled ligand-2E1 configurations from multiple docked orientations indicates the configurations with closest exposure of reactive centers to the oxyferryl heme to be correlated with observed metabolites with proper consideration of H-abstraction energetics. DFT assessment of relative radical energetics is directly compared with differential H-abstraction activation energetics by compound I and by a p-nitrosophenoxy radical compound I surrogate for the specific case of methoxyflurane and is shown to be in good agreement.
Collapse
Affiliation(s)
- Jin-Young Park
- Molecular Research Institute, 2495 Old Middlefield Way, Mountain View, California 94043, USA
| | | |
Collapse
|
43
|
Guengerich FP, Hanna IH, Martin MV, Gillam EMJ. Role of glutamic acid 216 in cytochrome P450 2D6 substrate binding and catalysis. Biochemistry 2003; 42:1245-53. [PMID: 12564927 DOI: 10.1021/bi027085w] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human cytochrome P450 (P450) 2D6 is an important enzyme involved in the metabolism of drugs, many of which are amines or contain other basic nitrogen atoms. Asp301 has generally been considered to be involved in electrostatic docking with the basic substrates, on the basis of previous modeling studies and site-directed mutagenesis. Substitution of Glu216 with a residue other than Asp strongly attenuated the binding of quinidine, bufuralol, and several other P450 2D6 ligands. Catalytic activity with the substrates bufuralol and 4-methoxyphenethylamine was strongly inhibited by neutral or basic mutations at Glu216 (>95%), to the same extent as the substitution of Asn at Asp301. Unlike the Asp301 mutants, the Gln216 mutant (E216Q) retained 40% enzyme efficiency with the substrate spirosulfonamide, devoid of basic nitrogen, suggesting that the substitutions at Glu216 affect binding of amine substrates more than other catalytic steps. Attempts to induce catalytic specificity toward new substrates by substitutions at Asp301 and Glu216 were unsuccessful. Collectively, the results provide evidence for electrostatic interaction of amine substrates with Glu216, and we propose that both of these acidic residues plus at least another residue(s) is (are) involved in binding the repertoire of P450 2D6 ligands.
Collapse
Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
| | | | | | | |
Collapse
|
44
|
Abstract
Cytochrome P450 (P450) reactions are of interest because of their relevance to the oxidative metabolism of drugs, steroids, carcinogens, and other chemicals. One of the considerations about functional characterization is which steps of the catalytic cycle are rate-limiting. Detailed analysis indicates that several different steps can be rate-limiting with individual P450 reactions. N-Dealkylation of para-substituted N,N-dimethylanilines is a function of the electron withdrawing/donating properties of the substituent and the oxidation-reduction potential of the substrate, supporting a role in rate-limiting electron transfer from substrate to the high valent P450. In the oxidations of ethanol and acetaldehyde by human P450 2E1, a step following product formation must be the slow step (but not product release per se). Several oxidations catalyzed by human P450s 1A2 and 2D6 show slow C-H bond breaking, and apparent high-valent iron complexes accumulate in the reaction steady-state. Kinetic simulations were used to test the suitability of potential schemes and to probe the effects of changes in individual reaction steps.
Collapse
|