1
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Qureshi M, Mokkawes T, Cao Y, de Visser SP. Mechanism of the Oxidative Ring-Closure Reaction during Gliotoxin Biosynthesis by Cytochrome P450 GliF. Int J Mol Sci 2024; 25:8567. [PMID: 39201254 PMCID: PMC11354885 DOI: 10.3390/ijms25168567] [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: 06/26/2024] [Revised: 07/30/2024] [Accepted: 08/02/2024] [Indexed: 09/02/2024] Open
Abstract
During gliotoxin biosynthesis in fungi, the cytochrome P450 GliF enzyme catalyzes an unusual C-N ring-closure step while also an aromatic ring is hydroxylated in the same reaction cycle, which may have relevance to drug synthesis reactions in biotechnology. However, as the details of the reaction mechanism are still controversial, no applications have been developed yet. To resolve the mechanism of gliotoxin biosynthesis and gain insight into the steps leading to ring-closure, we ran a combination of molecular dynamics and density functional theory calculations on the structure and reactivity of P450 GliF and tested a range of possible reaction mechanisms, pathways and models. The calculations show that, rather than hydrogen atom transfer from the substrate to Compound I, an initial proton transfer transition state is followed by a fast electron transfer en route to the radical intermediate, and hence a non-synchronous hydrogen atom abstraction takes place. The radical intermediate then reacts by OH rebound to the aromatic ring to form a biradical in the substrate that, through ring-closure between the radical centers, gives gliotoxin products. Interestingly, the structure and energetics of the reaction mechanisms appear little affected by the addition of polar groups to the model and hence we predict that the reaction can be catalyzed by other P450 isozymes that also bind the same substrate. Alternative pathways, such as a pathway starting with an electrophilic attack on the arene to form an epoxide, are high in energy and are ruled out.
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Affiliation(s)
| | | | | | - Sam P. de Visser
- Manchester Institute of Biotechnology, Department of Chemical Engineering, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK (Y.C.)
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2
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Hou Z, Li Y, Zheng M, Liu X, Zhang Q, Wang W. Regioselective oxidation of heterocyclic aromatic hydrocarbons catalyzed by cytochrome P450: A case study of carbazole. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 258:114964. [PMID: 37121081 DOI: 10.1016/j.ecoenv.2023.114964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 04/11/2023] [Accepted: 04/26/2023] [Indexed: 05/22/2023]
Abstract
Recently there are increasing interests in accurately evaluating the health effects of heterocyclic PAHs. However, the activation mechanism and possible metabolites of heterocyclic PAHs catalyzed by human CYP1A1 is still elusive to a great extent. Here, leveraged to high level QM/MM calculations, the corresponding activation pathways of a representative heterocyclic PAHs, carbazole, were systematically explored. The first stage is electrophilic addition or hydrogen abstraction from N-H group. Electrophilic addition was evidenced to be more feasible and regioselectivity at C3 and C4 sites were identified. Correlations between energy barriers and key structural/electrostatic parameters reveal that O-Cα distance and Fe-O-Cα angle are the main origin for the catalytic regioselectivity. Electrophilic addition was determined as the rate-determining step and the subsequent possible reactions include epoxidation, NIH shift (the hydrogen migration from the site of hydroxylation to the adjacent carbon) and proton shuttle. The corresponding products are epoxides, ketones and hydroxylated carbazoles, respectively. The main metabolites (hydroxylated carbazoles) are estimated to be more toxic than carbazole. The regioselectivity of carbazole activated by CYP1A1 is different from the environmental processes (gas and aqueous phase). Collectively, these results will inform the in-depth understanding the metabolic processes of heterocyclic PAHs and aid the accurate evaluation of their health effects.
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Affiliation(s)
- Zexi Hou
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Yanwei Li
- Environment Research Institute, Shandong University, Qingdao 266237, PR China; Shenzhen Research Institute, Shandong University, Shenzhen 518057, PR China.
| | - Mingna Zheng
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Xinning Liu
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Qingzhu Zhang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
| | - Wenxing Wang
- Environment Research Institute, Shandong University, Qingdao 266237, PR China
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3
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Liu S, Hirao H. Energy Decomposition Analysis of the Nature of Coordination Bonding at the Heme Iron Center in Cytochrome P450 Inhibition. Chem Asian J 2022; 17:e202200360. [PMID: 35514038 DOI: 10.1002/asia.202200360] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 04/26/2022] [Indexed: 11/11/2022]
Abstract
Drug compounds or their metabolic intermediates (MIs) sometimes inhibit the function of cytochrome P450 enzymes (P450s) by forming a coordination bond with the Fe(III) heme or Fe(II) heme of P450s. Such inhibition is one of the major causes of drug-drug interactions (DDIs), a subject of longstanding academic and practical interest. However, such coordination bonding is not fully understood at the quantum mechanical level, thus hampering rational improvement of the accuracy of DDI-related predictions. In this work, we employed density functional theory (DFT) and the generalized Kohn-Sham energy decomposition analysis (GKS-EDA) scheme to investigate the nature of the coordination bonding formed in the reversible and quasi-irreversible inhibition of P450s. The GKS-EDA results highlighted a previously unrecognized role of the electron correlation effect in P450 inhibition. The correlation effect tends to be larger in Fe(II) complexes of MI-type inhibitors and is particularly prominent for the nitrosoalkane ligand. An additional natural bond orbital (NBO) analysis provided insight into the relative significance of the σ donation and π backdonation effects in various heme-inhibitor complexes.
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Affiliation(s)
- Shuyang Liu
- The Chinese University of Hong Kong - Shenzhen, School of Life and Health Sciences, CHINA
| | - Hajime Hirao
- The Chinese University of Hong Kong - Shenzhen, School of Life and Health Sciences, …, Shenzhen, CHINA
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4
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Qin D, Dong L, Yang L. Theoretical study of thiazole activation in sudoxicam and meloxicam: Reaction center, biotransformation, and methyl effects. J CHIN CHEM SOC-TAIP 2022. [DOI: 10.1002/jccs.202100470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Dan Qin
- Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province China West Normal University Nanchong Sichuan China
| | - Lu Dong
- Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province China West Normal University Nanchong Sichuan China
| | - Lijun Yang
- Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province China West Normal University Nanchong Sichuan China
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School Sichuan University Chengdu Sichuan China
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5
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Kapoor S, Dubey G, Khatun S, Bharatam PV. Remdesivir: Mechanism of Metabolic Conversion from Prodrug to Drug. Curr Drug Metab 2021; 23:73-81. [PMID: 34963432 DOI: 10.2174/1389200223666211228160314] [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: 09/29/2021] [Revised: 10/25/2021] [Accepted: 12/01/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND Remdesivir (GS-5734) has emerged as a promising drug during the challenging times of COVID-19 pandemic. Being a prodrug, it undergoes several metabolic reactions before converting to its active triphosphate metabolite. It is important to establish the atomic level details and explore the energy profile of the prodrug to drug conversion process. METHODS In this work, Density Functional Theory (DFT) calculations were performed to explore the entire metabolic path. Further, the potential energy surface (PES) diagram for the conversion of prodrug remdesivir to its active metabolite was established. The role of catalytic triad of Hint1 phosphoramidase enzyme in P-N bond hydrolysis was also studied on a model system using combined molecular docking and quantum mechanics approach. RESULTS The overall energy of reaction is 11.47 kcal/mol exergonic and the reaction proceeds through many steps requiring high activation energies. In the absence of a catalyst, the P-N bond breaking step requires 41.78 kcal/mol, which is reduced to 14.26 kcal/mol in a catalytic environment. CONCLUSION The metabolic pathways of model system of remdesivir (MSR) were completely explored completely and potential energy surface diagrams at two levels of theory, B3LYP/6-311++G(d, p) and B3LYP/6-31+G(d), were established and compared. The results highlight the importance of an additional water molecule in the metabolic reaction. The P-N bond cleavage step of the metabolic process requires the presence of an enzymatic environment.
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Affiliation(s)
- Saumya Kapoor
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector - 67, S. A. S. Nagar (Mohali), 160062 Punjab, India
| | - Gurudutt Dubey
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector - 67, S. A. S. Nagar (Mohali), 160062 Punjab, India
| | - Samima Khatun
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector - 67, S. A. S. Nagar (Mohali), 160062 Punjab, India
| | - Prasad V Bharatam
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector - 67, S. A. S. Nagar (Mohali), 160062 Punjab, India
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6
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Jaladanki CK, Khatun S, Gohlke H, Bharatam PV. Reactive Metabolites from Thiazole-Containing Drugs: Quantum Chemical Insights into Biotransformation and Toxicity. Chem Res Toxicol 2021; 34:1503-1517. [PMID: 33900062 DOI: 10.1021/acs.chemrestox.0c00450] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Drugs containing thiazole and aminothiazole groups are known to generate reactive metabolites (RMs) catalyzed by cytochrome P450s (CYPs). These RMs can covalently modify essential cellular macromolecules and lead to toxicity and induce idiosyncratic adverse drug reactions. Molecular docking and quantum chemical hybrid DFT study were carried out to explore the molecular mechanisms involved in the biotransformation of thiazole (TZ) and aminothiazole (ATZ) groups leading to RM epoxide, S-oxide, N-oxide, and oxaziridine. The energy barrier required for the epoxidation is 13.63 kcal/mol, that is lower than that of S-oxidation, N-oxidation, and oxaziridine formation (14.56, 17.90, and 20.20, kcal/mol respectively). The presence of the amino group in ATZ further facilitates all the metabolic pathways, for example, the barrier for the epoxidation reaction is reduced by ∼2.5 kcal/mol. Some of the RMs/their isomers are highly electrophilic and tend to form covalent bonds with nucleophilic amino acids, finally leading to the formation of metabolic intermediate complexes (MICs). The energy profiles of these competitive pathways have also been explored.
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Affiliation(s)
- Chaitanya K Jaladanki
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector -67, S. A. S. Nagar (Mohali), 160 062 Punjab, India
| | - Samima Khatun
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector -67, S. A. S. Nagar (Mohali), 160 062 Punjab, India
| | - Holger Gohlke
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.,Forschungszentrum Jülich GmbH, John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), and Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Wilhelm-Johnen-Straße, 52425 Jülich, Germany
| | - Prasad V Bharatam
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector -67, S. A. S. Nagar (Mohali), 160 062 Punjab, India
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7
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Mirzaei MS, Ivanov MV, Taherpour AA, Mirzaei S. Mechanism-Based Inactivation of Cytochrome P450 Enzymes: Computational Insights. Chem Res Toxicol 2021; 34:959-987. [PMID: 33769041 DOI: 10.1021/acs.chemrestox.0c00483] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mechanism-based inactivation (MBI) refers to the metabolic bioactivation of a xenobiotic by cytochrome P450s to a highly reactive intermediate which subsequently binds to the enzyme and leads to the quasi-irreversible or irreversible inhibition. Xenobiotics, mainly drugs with specific functional units, are the major sources of MBI. Two possible consequences of MBI by medicinal compounds are drug-drug interaction and severe toxicity that are observed and highlighted by clinical experiments. Today almost all of these latent functional groups (e.g., thiophene, furan, alkylamines, etc.) are known, and their features and mechanisms of action, owing to the vast experimental and theoretical studies, are determined. In the past decade, molecular modeling techniques, mostly density functional theory, have revealed the most feasible mechanism that a drug undergoes by P450 enzymes to generate a highly reactive intermediate. In this review, we provide a comprehensive and detailed picture of computational advances toward the elucidation of the activation mechanisms of various known groups with MBI activity. To this aim, we briefly describe the computational concepts to carry out and analyze the mechanistic investigations, and then, we summarize the studies on compounds with known inhibition activity including thiophene, furan, alkylamines, terminal acetylene, etc. This study can be reference literature for both theoretical and experimental (bio)chemists in several different fields including rational drug design, the process of toxicity prevention, and the discovery of novel inhibitors and catalysts.
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Affiliation(s)
- M Saeed Mirzaei
- Department of Organic Chemistry, Faculty of Chemistry, Razi University, Kermanshah, Iran 67149-67346
| | - Maxim V Ivanov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Avat Arman Taherpour
- Department of Organic Chemistry, Faculty of Chemistry, Razi University, Kermanshah, Iran 67149-67346.,Medical Biology Research Centre, University of Medical Sciences, Kermanshah, Iran 67149-67346
| | - Saber Mirzaei
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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8
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Importance of substituents in ring opening: a DFT study on a model reaction of thiazole to thioamide. J Mol Model 2021; 27:89. [PMID: 33611758 DOI: 10.1007/s00894-021-04704-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 02/04/2021] [Indexed: 02/05/2023]
Abstract
Thiazole ring is an important active molecular skeleton of drugs. Thiazole in natural products and drugs are usually harmlessly eliminated. However, hepatotoxic reactions may occur due to the biological activation of thiazole to produce reactive thioamide. A typical example is hepatotoxic sudoxicam and safety meloxicam. The only structural difference between them is a methyl group on C5 position of thiazole in meloxicam. The molecular basis for the difference remains unknown and the bioactivation mechanism of the thiazole ring is still obscure. Quantum chemical calculations were performed to elucidate the activation mechanism of the thiazole ring under P450 catalysis, and the influence of the substituents on the activation pathways of thiazole ring was also studied. The calculated results show that the activation of thiazole is closely related to the substituents on the thiazole and spin state of Cpd I. The thiazole and substituted thiazole directly open the ring when catalyzed by doublet spin state Cpd I that catalyzed by the quartet spin state Cpd I can open the ring directly or indirectly, which is related to the substituents. Thiazoles modified with electron-donating substituents mainly undergo direct ring opening, while thiazoles modified with electron-withdrawing groups or weak electron-donating groups mainly undergo indirect ring-opening process accompanied by intermediate formation. The research results laid the foundation for the design of thiazole ring drugs, and also laid a theoretical foundation for the study of reducing the toxicity of thiazole ring drugs.
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9
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Emhoff KA, Balaraman L, Salem AM, Mudarmah KI, Boyd WC. Coordination chemistry of organic nitric oxide derivatives. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2019.06.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Theoretical study on the mechanism of N- and α-carbon oxidation of lapatinib catalyzed by cytochrome P450 monooxygenase. J Mol Model 2019; 25:225. [PMID: 31312984 DOI: 10.1007/s00894-019-4125-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 07/07/2019] [Indexed: 10/26/2022]
Abstract
Lapatinib, an orally active dual tyrosine kinase inhibitor, is efficacious in combination therapy with capecitabine for advanced metastatic breast cancer. Despite its importance, it has been associated with hepatotoxicity observed in clinical trials and postmarketing surveillance. The mechanisms of hepatotoxicity at the chemical and cellular levels may link to drug metabolism. In this study, the N- and α-carbon oxidation processes of lapatinib catalyzed by CYP3A4 were explored by density functional theory method. The calculation results show that oxidation of C6 is the primary metabolic process and carboxylic acid is the main metabolic product. Both hydroxylation of C8 and subsequent formation of primary amines are feasible. However, it is not easy for the primary amines to form active metabolites nitroso, which indicates that there are other paths for the production of nitroso. Carboxylic acid is not the main metabolite of N7 oxidation because of higher hydrolysis energy barrier of intermediate nitrone. It is worthy to study subsequent N-hydroxylation and its downstream reaction, which may be the main pathway for the formation of nitroso. These results lay the foundation for drug design and optimization.
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11
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Nishimuta H, Sato K, Watanabe T, Yabuki M. Time-dependent inhibition (TDI) of CYP1A2 by a CYP3A4-mediated reactive metabolite: proposal for a novel mechanism of irreversible TDI by a non-suicide substrate. Xenobiotica 2018; 49:636-645. [PMID: 29889646 DOI: 10.1080/00498254.2018.1488011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
1. The purpose of this study was to clarify the mechanism of DSP-1053 time-dependent inhibition (TDI) for CYP1A2. 2. DSP-1053 inhibited time- and concentration-dependently CYP1A2 activity in human liver microsomes even in a dilution assay. However, DSP-1053 was not metabolized by recombinant human CYP1A2. These findings indicate that the inhibitory effect of DSP-1053 on CYP1A2 does not follow a general mechanism-based inhibition (MBI) because it did not seem to be a suicide substrate. 3. In fact, CYP1A2 was not inhibited with DSP-1053 pre-incubation in recombinant human CYP1A2. On the other hand, CYP1A2 was potently inhibited after pre-incubation with DSP-1053 in a mixture of human recombinant CYP1A2 and CYP3A4. In addition, DSP-1053 TDI of CYP1A2 in human liver microsomes was drastically reduced not only by addition of a CYP3A4 inhibitor, but also by addition of potassium cyanide (KCN), which is a trapping agent for iminium ions. We also confirmed in this study that CYP1A2 suicide inhibition by DSP-1053 metabolites generated by CYP3A4 had only minimal role in DSP-1053 TDI of CYP1A2. 4. In conclusion, a possible mechanism for DSP-1053 TDI of CYP1A2 is that DSP-1053 iminium ion, which is generated by CYP3A4, departs from CYP3A4 without inhibiting it and covalently binds to CYP1A2.
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Affiliation(s)
- Haruka Nishimuta
- a Preclinical Research Unit , Sumitomo Dainippon Pharma Co. Ltd. , Osaka , Japan
| | - Kimihiko Sato
- a Preclinical Research Unit , Sumitomo Dainippon Pharma Co. Ltd. , Osaka , Japan
| | - Takao Watanabe
- a Preclinical Research Unit , Sumitomo Dainippon Pharma Co. Ltd. , Osaka , Japan
| | - Masashi Yabuki
- a Preclinical Research Unit , Sumitomo Dainippon Pharma Co. Ltd. , Osaka , Japan
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12
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Mirzaei S, Taherpour AA, Khalilian H. Importance of Azo-Hydrazo Tautomerization in the Oxidative Degradation of Procarbazine by Cytochrome P450: Computational Insights. ChemistrySelect 2018. [DOI: 10.1002/slct.201800633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Saber Mirzaei
- Department of Chemistry; Marquette University, 1414 W. Clybourn St., Milwaukee; WI 53233 USA
| | - Avat Arman Taherpour
- Department of Organic Chemistry; Faculty of Chemistry; Razi University; 67149-67346, Kermanshah, Iran; Medical Biology Research Centre, Kermanshah University of Medical Sciences, Kermanshah Iran
| | - Hossein Khalilian
- Department of Chemistry; University of British Columbia; Okanagan; 3247 University Way, Kelowna, British Columbia V1 V 1 V7 Canada
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13
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Alberro N, Torrent-Sucarrat M, Arrieta A, Rubiales G, Cossío FP. Density Functional Theory Study on the Demethylation Reaction between Methylamine, Dimethylamine, Trimethylamine, and Tamoxifen Catalyzed by a Fe(IV)-Oxo Porphyrin Complex. J Phys Chem A 2018; 122:1658-1671. [PMID: 29320849 DOI: 10.1021/acs.jpca.7b10654] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In this work, we studied computationally the N-demethylation reaction of methylamine, dimethylamine, and trimethylamine as archetypal examples of primary, secondary, and tertiary amines catalyzed by high-field low-spin Fe-containing enzymes such as cytochromes P450. Using DFT calculations, we found that the expected C-H hydroxylation process was achieved for trimethylamine. When dimethylamine and methylamine were studied, two different reaction mechanisms (C-H hydroxylation and a double hydrogen atom transfer) were computed to be energetically accessible and both are equally preferred. Both processes led to the formation of formaldehyde and the N-demethylated substrate. Finally, as an illustrative example, the relative contribution of the three primary oxidation routes of tamoxifen was rationalized through energetic barriers obtained from density functional calculations and docking experiments involving CYP3A4 and CYP2D6 isoforms. We found that the N-demethylation process was the intrinsically favored one, whereas other oxidation reactions required most likely preorganization imposed by the residues close to the active sites.
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Affiliation(s)
- Nerea Alberro
- Department of Organic Chemistry I, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Centro de Innovación en Química Avanzada (ORFEO-CINQA) , Manuel Lardizabal Ibilbidea 3, 20018 San Sebastián/Donostia, Spain
| | - Miquel Torrent-Sucarrat
- Department of Organic Chemistry I, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Centro de Innovación en Química Avanzada (ORFEO-CINQA) , Manuel Lardizabal Ibilbidea 3, 20018 San Sebastián/Donostia, Spain.,Donostia International Physics Center (DIPC) , Manuel Lardizabal Ibilbidea 4, 20018 San Sebastián/Donostia, Spain.,Ikerbasque, Basque Foundation for Science , María Díaz de Haro 3, 6°, 48013 Bilbao, Spain
| | - Ana Arrieta
- Department of Organic Chemistry I, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Centro de Innovación en Química Avanzada (ORFEO-CINQA) , Manuel Lardizabal Ibilbidea 3, 20018 San Sebastián/Donostia, Spain
| | - Gloria Rubiales
- Department of Organic Chemistry I, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Centro de Innovación en Química Avanzada (ORFEO-CINQA) , Manuel Lardizabal Ibilbidea 3, 20018 San Sebastián/Donostia, Spain
| | - Fernando P Cossío
- Department of Organic Chemistry I, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Centro de Innovación en Química Avanzada (ORFEO-CINQA) , Manuel Lardizabal Ibilbidea 3, 20018 San Sebastián/Donostia, Spain.,Donostia International Physics Center (DIPC) , Manuel Lardizabal Ibilbidea 4, 20018 San Sebastián/Donostia, Spain
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14
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Jaladanki CK, Shaikh A, Bharatam PV. Biotransformation of Isoniazid by Cytochromes P450: Analyzing the Molecular Mechanism using Density Functional Theory. Chem Res Toxicol 2017; 30:2060-2073. [DOI: 10.1021/acs.chemrestox.7b00129] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chaitanya K. Jaladanki
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector -67, S. A. S. Nagar, Mohali, 160 062 Punjab, India
| | - Akbar Shaikh
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector -67, S. A. S. Nagar, Mohali, 160 062 Punjab, India
| | - Prasad V. Bharatam
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector -67, S. A. S. Nagar, Mohali, 160 062 Punjab, India
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15
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El-Sherbeni AA, El-Kadi AOS. Microsomal cytochrome P450 as a target for drug discovery and repurposing. Drug Metab Rev 2016; 49:1-17. [DOI: 10.1080/03602532.2016.1257021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Ahmed A. El-Sherbeni
- Faculty of Pharmacy and Pharmaceutical Sciences, 2142J Katz Group-Rexall Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, Canada
| | - Ayman O. S. El-Kadi
- Faculty of Pharmacy and Pharmaceutical Sciences, 2142J Katz Group-Rexall Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, Canada
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16
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Jaladanki CK, Taxak N, Varikoti RA, Bharatam PV. Toxicity Originating from Thiophene Containing Drugs: Exploring the Mechanism using Quantum Chemical Methods. Chem Res Toxicol 2015; 28:2364-76. [PMID: 26574776 DOI: 10.1021/acs.chemrestox.5b00364] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Drug metabolism of thiophene containing substrates by cytochrome P450s (CYP450) leads to toxic side effects, for example, nephrotoxicity (suprofen, ticlopidine), hepatotoxicity (tienilic acid), thrombotic thrombocytopenic purpura (clopidogrel), and aplastic anemia (ticlopidine). The origin of toxicity in these cases has been attributed to two different CYP450 mediated metabolic reactions: S-oxidation and epoxidation. In this work, the molecular level details of the bioinorganic chemistry associated with the generation of these competitive reactions are reported. Density functional theory was utilized (i) to explore the molecular mechanism for S-oxidation and epoxidation using the radical cationic center Cpd I [(iron(IV)-oxo-heme porphine system with SH(-) as the axial ligand, to mimic CYP450s] as the model oxidant, (ii) to establish the 3D structures of the reactants, transition states, and products on both the metabolic pathways, and (iii) to examine the potential energy (PE) profile for both the pathways to determine the energetically preferred toxic metabolite formation. The energy barrier required for S-oxidation was observed to be 14.75 kcal/mol as compared to that of the epoxidation reaction (13.23 kcal/mol) on the doublet PE surface of Cpd I. The formation of the epoxide metabolite was found to be highly exothermic (-23.24 kcal/mol), as compared to S-oxidation (-8.08 kcal/mol). Hence, on a relative scale the epoxidation process was observed to be thermodynamically and kinetically more favorable. The energy profiles associated with the reactions of the S-oxide and epoxide toxic metabolites were also explored. This study helps in understanding the CYP450-catalyzed toxic reactions of drugs containing the thiophene ring at the atomic level.
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Affiliation(s)
- Chaitanya K Jaladanki
- Department of Medicinal Chemistry and ‡Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research (NIPER) , Sector-67, S. A. S. Nagar (Mohali), 160 062 Punjab, India
| | - Nikhil Taxak
- Department of Medicinal Chemistry and ‡Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research (NIPER) , Sector-67, S. A. S. Nagar (Mohali), 160 062 Punjab, India
| | - Rohith A Varikoti
- Department of Medicinal Chemistry and ‡Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research (NIPER) , Sector-67, S. A. S. Nagar (Mohali), 160 062 Punjab, India
| | - Prasad V Bharatam
- Department of Medicinal Chemistry and ‡Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research (NIPER) , Sector-67, S. A. S. Nagar (Mohali), 160 062 Punjab, India
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Li XX, Wang Y, Zheng QC, Zhang HX. Detoxification of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by cytochrome P450 enzymes: A theoretical investigation. J Inorg Biochem 2015; 154:21-8. [PMID: 26544505 DOI: 10.1016/j.jinorgbio.2015.10.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 10/12/2015] [Accepted: 10/19/2015] [Indexed: 11/24/2022]
Abstract
Two types of detoxification routes, N-demethylation to form 4-phenyl-1,2,3,6-tetrahydropyridine (PTP) and aromatic hydroxylation to generate 4-(4'-hydroxyphenyl)-1-methyl-1,2,3,6-tetrahydropyridine (MPTP-OH), for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mediated by Compound I (Cpd I) of cytochrome P450 are investigated theoretically using hybrid density functional calculations. Quantum chemical results reveal that for the N-demethylation, the initial C-H bond activation is achieved via a hydrogen atom transfer (HAT) mechanism. This is followed by a subsequent O-rebound to yield the carbinolamine intermediate. Due to the nature of pericyclic reaction, the generated carbinolamine decomposes in a non-enzymatic aqueous environment with the assistance of water molecules, forming amine and hydrated formaldehyde. For the aromatic hydroxylation, an initial addition of Cpd I to the substrate occurs mainly through a side-on approach with a subsequent proton shuttle to form the phenol product. A comparison of the energy barriers for both routes indicates that the N-demethylation (7.5/5.7kcal/mol for the quartet/doublet state in solvent) is thermodynamically more favorable than the aromatic hydroxylation process (14.9/14.8kcal/mol for the quartet/doublet state in solvent). This trend is in good agreement with the experimental product distribution, viz., the N-demethylation product PTP is more than the aromatic hydroxylation product MPTP-OH. Taken together, these observations not only enrich our knowledge on the mechanistic details of the N-dealkylation and the aromatic hydroxylation by P450s, but also provide certain insights into the metabolism of other analogous toxins.
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Affiliation(s)
- Xiao-Xi Li
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China; State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
| | - Yong Wang
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, People's Republic of China
| | - Qing-Chuan Zheng
- Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, Jilin University, Changchun 130023, People's Republic of China; State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.
| | - Hong-Xing Zhang
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
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Chuanprasit P, Goh SH, Hirao H. Benzyne Formation in the Mechanism-Based Inactivation of Cytochrome P450 by 1-Aminobenzotriazole and N-Benzyl-1-Aminobenzotriazole: Computational Insights. ACS Catal 2015. [DOI: 10.1021/acscatal.5b00423] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Pratanphorn Chuanprasit
- Division of Chemistry and
Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Shu Hui Goh
- Division of Chemistry and
Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Hajime Hirao
- Division of Chemistry and
Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
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Li XX, Zhang X, Zheng QC, Wang Y. Bio-activation of 4-alkyl analogs of 1,4-dihydropyridine mediated by cytochrome P450 enzymes. J Biol Inorg Chem 2015; 20:665-73. [DOI: 10.1007/s00775-015-1252-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 02/25/2015] [Indexed: 10/23/2022]
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Arfeen M, Patel DS, Abbat S, Taxak N, Bharatam PV. Importance of cytochromes in cyclization reactions: Quantum chemical study on a model reaction of proguanil to cycloguanil. J Comput Chem 2014; 35:2047-55. [DOI: 10.1002/jcc.23719] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Revised: 08/04/2014] [Accepted: 08/06/2014] [Indexed: 12/23/2022]
Affiliation(s)
- Minhajul Arfeen
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER); S. A. S. Nagar (Mohali) 160 062 Punjab India
| | - Dhilon S. Patel
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER); S. A. S. Nagar (Mohali) 160 062 Punjab India
| | - Sheenu Abbat
- Department of Pharmacoinformatics; National Institute of Pharmaceutical Education and Research (NIPER); S. A. S. Nagar (Mohali) 160 062 Punjab India
| | - Nikhil Taxak
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER); S. A. S. Nagar (Mohali) 160 062 Punjab India
| | - Prasad V. Bharatam
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER); S. A. S. Nagar (Mohali) 160 062 Punjab India
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Hirao H, Thellamurege N, Zhang X. Applications of density functional theory to iron-containing molecules of bioinorganic interest. Front Chem 2014; 2:14. [PMID: 24809043 PMCID: PMC4010748 DOI: 10.3389/fchem.2014.00014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 03/10/2014] [Indexed: 12/29/2022] Open
Abstract
The past decades have seen an explosive growth in the application of density functional theory (DFT) methods to molecular systems that are of interest in a variety of scientific fields. Owing to its balanced accuracy and efficiency, DFT plays particularly useful roles in the theoretical investigation of large molecules. Even for biological molecules such as proteins, DFT finds application in the form of, e.g., hybrid quantum mechanics and molecular mechanics (QM/MM), in which DFT may be used as a QM method to describe a higher prioritized region in the system, while a MM force field may be used to describe remaining atoms. Iron-containing molecules are particularly important targets of DFT calculations. From the viewpoint of chemistry, this is mainly because iron is abundant on earth, iron plays powerful (and often enigmatic) roles in enzyme catalysis, and iron thus has the great potential for biomimetic catalysis of chemically difficult transformations. In this paper, we present a brief overview of several recent applications of DFT to iron-containing non-heme synthetic complexes, heme-type cytochrome P450 enzymes, and non-heme iron enzymes, all of which are of particular interest in the field of bioinorganic chemistry. Emphasis will be placed on our own work.
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Affiliation(s)
- Hajime Hirao
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological UniversitySingapore, Singapore
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Hirao H, Thellamurege NM, Chuanprasit P, Xu K. Importance of H-abstraction in the final step of nitrosoalkane formation in the mechanism-based inactivation of cytochrome P450 by amine-containing drugs. Int J Mol Sci 2013; 14:24692-705. [PMID: 24351842 PMCID: PMC3876136 DOI: 10.3390/ijms141224692] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2013] [Revised: 11/27/2013] [Accepted: 11/29/2013] [Indexed: 11/29/2022] Open
Abstract
The metabolism of amine-containing drugs by cytochrome P450 enzymes (P450s) is prone to form a nitrosoalkane metabolic intermediate (MI), which subsequently coordinates to the heme iron of a P450, to produce a metabolic-intermediate complex (MIC). This type of P450 inhibition, referred to as mechanism-based inactivation (MBI), presents a serious concern in drug discovery processes. We applied density functional theory (DFT) to the reaction between N-methylhydroxylamine (NMH) and the compound I reactive species of P450, in an effort to elucidate the mechanism of the putative final step of the MI formation in the alkylamine metabolism. Our DFT calculations show that H-abstraction from the hydroxyl group of NMH is the most favorable pathway via which the nitrosoalkane intermediate is produced spontaneously. H-abstraction from the N–H bond was slightly less favorable. In contrast, N-oxidation and H-abstraction from the C–H bond of the methyl group had much higher energy barriers. Hence, if the conversion of NMH to nitrosoalkane is catalyzed by a P450, the reaction should proceed preferentially via H-abstraction, either from the O–H bond or from the N–H bond. Our theoretical analysis of the interaction between the MI and pentacoordinate heme moieties provided further insights into the coordination bond in the MIC.
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Affiliation(s)
- Hajime Hirao
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link 637371, Singapore.
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Taxak N, Kalra S, Bharatam PV. Mechanism-Based Inactivation of Cytochromes by Furan Epoxide: Unraveling the Molecular Mechanism. Inorg Chem 2013; 52:13496-508. [DOI: 10.1021/ic401907k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Nikhil Taxak
- Department
of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S. A. S. Nagar
(Mohali), 160 062 Punjab, India
| | - Sourav Kalra
- Department
of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S. A. S. Nagar
(Mohali), 160 062 Punjab, India
| | - Prasad V. Bharatam
- Department
of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S. A. S. Nagar
(Mohali), 160 062 Punjab, India
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Hirao H, Chuanprasit P, Cheong YY, Wang X. How is a metabolic intermediate formed in the mechanism-based inactivation of cytochrome P450 by using 1,1-dimethylhydrazine: hydrogen abstraction or nitrogen oxidation? Chemistry 2013; 19:7361-9. [PMID: 23592585 DOI: 10.1002/chem.201300689] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Indexed: 11/10/2022]
Abstract
A precise understanding of the mechanism-based inactivation of cytochrome P450 enzymes (P450s) at the quantum mechanical level should allow more reliable predictions of drug-drug interactions than those currently available. Hydrazines are among the molecules that act as mechanism-based inactivators to terminate the function of P450s, which are essential heme enzymes responsible for drug metabolism in the human body. Despite its importance, the mechanism explaining how a metabolic intermediate (MI) is formed from hydrazine is not fully understood. We used density functional theory (DFT) calculations to compare four possible mechanisms underlying the reaction between 1,1-dimethylhydrazine (or unsymmetrical dimethylhydrazine, UDMH) and the reactive compound I (Cpd I) intermediate of P450. Our DFT calculations provided a clear view on how an aminonitrene-type MI is formed from UDMH. In the most favorable pathway, hydrogen is spontaneously abstracted from the N2 atom of UDMH by Cpd I, followed by a second hydrogen abstraction from the N2 atom by Cpd II. Nitrogen oxidation of nitrogen atoms and hydrogen abstraction from the C-H bond of the methyl group were found to be less favorable than the hydrogen abstraction from the N-H bond. We also found that the reaction of protonated UDMH with Cpd I is rather sluggish. The aminonitrene-type MI binds to the ferric heme more strongly than a water molecule. This is consistent with the notion that the catalytic cycle of P450 is impeded when such an MI is produced through the P450-catalyzed reaction.
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Affiliation(s)
- Hajime Hirao
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
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Taxak N, Patel B, Bharatam PV. Carbene Generation by Cytochromes and Electronic Structure of Heme-Iron-Porphyrin-Carbene Complex: A Quantum Chemical Study. Inorg Chem 2013; 52:5097-109. [DOI: 10.1021/ic400010d] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Nikhil Taxak
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), S. A. S. Nagar (Mohali), 160 062 Punjab, India
| | - Bhargav Patel
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), S. A. S. Nagar (Mohali), 160 062 Punjab, India
| | - Prasad V. Bharatam
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), S. A. S. Nagar (Mohali), 160 062 Punjab, India
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Mechanistic insights into the bioactivation of phenacetin to reactive metabolites: A DFT study. COMPUT THEOR CHEM 2013. [DOI: 10.1016/j.comptc.2012.11.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Barbara JE, Kazmi F, Parkinson A, Buckley DB. Metabolism-Dependent Inhibition of CYP3A4 by Lapatinib: Evidence for Formation of a Metabolic Intermediate Complex with a Nitroso/Oxime Metabolite Formed via a Nitrone Intermediate. Drug Metab Dispos 2013; 41:1012-22. [DOI: 10.1124/dmd.113.051151] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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Taxak N, Dixit VA, Bharatam PV. Density functional study on the cytochrome-mediated S-oxidation: identification of crucial reactive intermediate on the metabolic path of thiazolidinediones. J Phys Chem A 2012; 116:10441-50. [PMID: 23025570 DOI: 10.1021/jp308023g] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
S-Oxidation is an important cytochrome P450 (CYP450)-catalyzed reaction, and the structural and energetic details of this process can only be studied by using quantum chemical methods. Thiazolidinedione (TZD) ring metabolism involving initial S-oxidation leads to the generation of reactive metabolites (RMs) and subsequent toxicity forcing the withdrawal of the glitazone class of drugs, thus, the study of the biochemical pathway of TZD ring metabolism is a subject of interest. The S-oxidation of the TZD ring and the formation of the isocyanate intermediate (ISC) was implicated as a possible pathway; however, there are several questions still unanswered in this biochemical pathway. The current study focuses on the CYP450-mediated S-oxidation, fate of the sulfoxide product (TZDSO), ring cleavage to ISC, and formation of nucleophilic adducts. The process of S-oxidation was explored by using Cpd I (iron(IV)-oxo porphyrin, to mimic CYP450) at TZVP/6-311+G(d) basis set. The barriers were calculated after incorporating dispersion and solvent corrections. The metabolic conversion from TZDSO to ISC (studied at B3LYP/6-311++G(2df,3pd)//B3LYP/6-31+G(d)) required a novel protonated intermediate, TZDSOH(+). The effect of higher basis sets (6-311+G(d,p), aug-cc-pvqz) on this conversion was studied. TZDSOH(+) was observed to be more reactive and thermodynamically accessible than ISC, indicating that TZDSOH(+) is the actual reactive intermediate leading to toxicity of the TZD class of compounds.
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Affiliation(s)
- Nikhil Taxak
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), S. A. S. Nagar (Mohali), 160 062 Punjab, India
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