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Rendić SP, Crouch RD, Guengerich FP. Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions. Arch Toxicol 2022; 96:2145-2246. [PMID: 35648190 PMCID: PMC9159052 DOI: 10.1007/s00204-022-03304-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 04/26/2022] [Indexed: 12/17/2022]
Abstract
This is an overview of the metabolic reactions of drugs, natural products, physiological compounds, and other (general) chemicals catalyzed by flavin monooxygenase (FMO), monoamine oxidase (MAO), NAD(P)H quinone oxidoreductase (NQO), and molybdenum hydroxylase enzymes (aldehyde oxidase (AOX) and xanthine oxidoreductase (XOR)), including roles as substrates, inducers, and inhibitors of the enzymes. The metabolism and bioactivation of selected examples of each group (i.e., drugs, “general chemicals,” natural products, and physiological compounds) are discussed. We identified a higher fraction of bioactivation reactions for FMO enzymes compared to other enzymes, predominately involving drugs and general chemicals. With MAO enzymes, physiological compounds predominate as substrates, and some products lead to unwanted side effects or illness. AOX and XOR enzymes are molybdenum hydroxylases that catalyze the oxidation of various heteroaromatic rings and aldehydes and the reduction of a number of different functional groups. While neither of these two enzymes contributes substantially to the metabolism of currently marketed drugs, AOX has become a frequently encountered route of metabolism among drug discovery programs in the past 10–15 years. XOR has even less of a role in the metabolism of clinical drugs and preclinical drug candidates than AOX, likely due to narrower substrate specificity.
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Affiliation(s)
| | - Rachel D Crouch
- College of Pharmacy and Health Sciences, Lipscomb University, Nashville, TN, 37204, USA
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, 37232-0146, USA
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Population Pharmacokinetics of Sulindac and Genetic Polymorphisms of FMO3 and AOX1 in Women with Preterm Labor. Pharm Res 2020; 37:44. [PMID: 31993760 DOI: 10.1007/s11095-020-2765-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2019] [Accepted: 01/16/2020] [Indexed: 10/25/2022]
Abstract
PURPOSE This prospective study aimed to evaluate the effects of genetic polymorphisms in sulindac-related metabolizing enzyme genes including FMO3 and AOX1 on the population pharmacokinetics of sulindac in 58 pregnant women with preterm labor. METHODS Plasma samples were collected at 1.5, 4, and 10 h after first oral administration of sulindac. Plasma concentrations of sulindac and its active metabolite (sulindac sulfide) were determined, and pharmacokinetic analysis was performed with NONMEM 7.3. RESULTS The mean maternal and gestational ages at the time of dosing were 32.5 ± 4.4 (range, 20-41) years and 27.4 ± 4.4 (range, 16.4-33.4) weeks, respectively. In the population pharmacokinetic analysis, one depot compartment model of sulindac with absorption lag time best described the data. The metabolism of sulindac and sulindac sulfide was described using Michaelis-Menten kinetics. In stepwise modeling, gestational age impacted volume of distribution (Vc), and FMO3 rs2266782 was shown by the Michaelis constant to affect conversion of sulindac sulfide to sulindac (KM32); these were retained in the final model. CONCLUSIONS Genetic polymorphisms of FMO3 and AOX1 could affect the pharmacokinetics of sulindac in women who undergo preterm labor. The results of this study could help clinicians develop individualized treatment plans for administering sulindac.
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Liu J, Lai L, Lin J, Zheng J, Nie X, Zhu X, Xue J, Liu T. Ranitidine and finasteride inhibit the synthesis and release of trimethylamine N-oxide and mitigates its cardiovascular and renal damage through modulating gut microbiota. Int J Biol Sci 2020; 16:790-802. [PMID: 32071549 PMCID: PMC7019130 DOI: 10.7150/ijbs.40934] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Accepted: 12/06/2019] [Indexed: 12/11/2022] Open
Abstract
Trimethylamine N-oxide (TMAO) leads to the development of cardiovascular and chronic kidney diseases, but there are currently no potent drugs that inhibit the production or toxicity of TMAO. In this study, high-fat diet-fed ApoE-/- mice were treated with finasteride, ranitidine, and andrioe. Subsequently, the distribution and quantity of gut microbiota in the faeces of the mice in each group were analysed using 16S rRNA sequencing of the V3+V4 regions. Pathological examination confirmed that both ranitidine and finasteride reduced atherosclerosis and renal damage in mice. HPLC analysis also indicated that ranitidine and finasteride significantly reduced the synthesis of TMAO and the TMAO precursor delta-Valerobetaine in their livers. The 16S rRNA sequencing showed that all 3 drugs significantly increased the richness and diversity of gut microbiota in the model mice. Bioinformatic analysis revealed that the faeces of mice treated with ranitidine and finasteride, had significant increases in the number of microbes in the families g_Helicobacter, f_Desulfovibrionaceae, Mucispirillum_schaedleri_ASF457, and g_Blautia, whereas the relative abundances of microbes in the families Enterobacter_sp._IPC1-8 and g_Bacteroides were significantly reduced. The microbiota metabolic pathways, such as nucleotide and cofactor and vitamin metabolism were also significantly increased, whereas the activities of metabolic signalling pathways related to glycan biosynthesis and metabolism and cardiovascular diseases were significantly reduced. Therefore, our study indicates that in addition to their known pharmacological effects, ranitidine and finasteride also exhibit potential cardiovascular and renal protective effects. They inhibit the synthesis and metabolism of TMAO and delay the deposition of lipids and endotoxins through improving the composition of the gut microbiota.
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Affiliation(s)
- Junfeng Liu
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Lingyun Lai
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Jiajia Lin
- Shanghai Geriatric Institute of Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 200031, China
| | - Jiajia Zheng
- Shanghai Geriatric Institute of Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 200031, China
| | - Xiaoli Nie
- Shanghai Geriatric Institute of Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 200031, China
| | - Xiaoye Zhu
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Jun Xue
- Division of Nephrology, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Te Liu
- Shanghai Geriatric Institute of Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai 200031, China
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4
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Phillips IR, Shephard EA. Flavin-containing monooxygenase 3 (FMO3): genetic variants and their consequences for drug metabolism and disease. Xenobiotica 2019; 50:19-33. [DOI: 10.1080/00498254.2019.1643515] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ian R. Phillips
- Research Department of Structural and Molecular Biology, University College London, London, UK
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Elizabeth A. Shephard
- Research Department of Structural and Molecular Biology, University College London, London, UK
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5
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Nguyen PTT, Parvez MM, Kim MJ, Yoo SE, Ahn S, Ghim JL, Shin JG. Physiologically Based Pharmacokinetic Modeling Approach to Predict Drug-Drug Interactions With Ethionamide Involving Impact of Genetic Polymorphism on FMO3. J Clin Pharmacol 2019; 59:880-889. [PMID: 30690726 DOI: 10.1002/jcph.1378] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 01/02/2019] [Indexed: 11/06/2022]
Abstract
The widely used second-line antituberculosis drug ethionamide shows wide interindividual variability in its disposition; however, the relevant factors affecting this phenomenon have not been characterized. We previously reported the major contribution of flavin-containing monooxygenase 3 (FMO3) in the reductive elimination pathway of ethionamide. In this study, ethionamide metabolism was potentially inhibited by methimazole in vitro. The drug-drug interaction leading to methimazole affecting the disposition of ethionamide mediated by FMO3 was then quantitated using a bottom-up approach with a physiologically based pharmacokinetic framework. The maximum concentration (Cmax ) and area under the curve (AUC) of ethionamide were estimated to increase by 13% and 16%, respectively, when coadministered with methimazole. Subsequently, we explored the effect of FMO3 genetic polymorphism on metabolic capacity, by constructing 2 common functional variants, Lys158 -FMO3 and Gly308 -FMO3. Compared to the wild type, recombinant Lys158 -FMO3 and Gly308 -FMO3 variants significantly decreased the intrinsic clearance of ethionamide by 2% and 24%, respectively. Two prevalent functional variants of FMO3 were predicted to affect ethionamide disposition, with mean ratios of Cmax and AUC of up to 1.5 and 1.7, respectively, in comparison with the wild type. In comparing single ethionamide administration with the wild type, simulations of the combined effects of comedications and FMO3 genetic polymorphism estimated that the Cmax and AUC ratios of ethionamide increased up to 1.7 and 2.0, respectively. These findings suggested that FMO3-mediated drug-drug interaction and genetic polymorphism could be important determinants of interindividual heterogeneity in ethionamide disposition that need to be considered comprehensively to optimize the personalized dosing of ethionamide.
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Affiliation(s)
- Phuong Thi Thu Nguyen
- Department of Pharmacology and Clinical Pharmacology, PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.,Center for Personalized Precision Medicine of Tuberculosis, Inje University College of Medicine, Busan, Republic of Korea.,Faculty of Pharmacy, Hai Phong University of Medicine and Pharmacy, Hai Phong, Vietnam
| | - Md Masud Parvez
- Department of Pharmacology and Clinical Pharmacology, PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.,Center for Personalized Precision Medicine of Tuberculosis, Inje University College of Medicine, Busan, Republic of Korea
| | - Min Jung Kim
- Department of Pharmacology and Clinical Pharmacology, PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.,Center for Personalized Precision Medicine of Tuberculosis, Inje University College of Medicine, Busan, Republic of Korea
| | - Sung Eun Yoo
- Department of Pharmacology and Clinical Pharmacology, PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.,Center for Personalized Precision Medicine of Tuberculosis, Inje University College of Medicine, Busan, Republic of Korea
| | - Sangzin Ahn
- Department of Pharmacology and Clinical Pharmacology, PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.,Center for Personalized Precision Medicine of Tuberculosis, Inje University College of Medicine, Busan, Republic of Korea
| | - Jong-Lyul Ghim
- Department of Pharmacology and Clinical Pharmacology, PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.,Center for Personalized Precision Medicine of Tuberculosis, Inje University College of Medicine, Busan, Republic of Korea.,Department of Clinical Pharmacology, Inje University Busan Paik Hospital, Busan, Republic of Korea
| | - Jae-Gook Shin
- Department of Pharmacology and Clinical Pharmacology, PharmacoGenomics Research Center, Inje University College of Medicine, Busan, Republic of Korea.,Center for Personalized Precision Medicine of Tuberculosis, Inje University College of Medicine, Busan, Republic of Korea.,Department of Clinical Pharmacology, Inje University Busan Paik Hospital, Busan, Republic of Korea
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6
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Teitelbaum AM, Murphy SE, Akk G, Baker TB, Germann A, von Weymarn LB, Bierut LJ, Goate A, Kharasch ED, Bloom AJ. Nicotine dependence is associated with functional variation in FMO3, an enzyme that metabolizes nicotine in the brain. THE PHARMACOGENOMICS JOURNAL 2018; 18:136-143. [PMID: 28290528 PMCID: PMC5599305 DOI: 10.1038/tpj.2016.92] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 10/20/2016] [Accepted: 12/08/2016] [Indexed: 12/16/2022]
Abstract
A common haplotype of the flavin-containing monooxygenase gene FMO3 is associated with aberrant mRNA splicing, a twofold reduction in in vivo nicotine N-oxidation and reduced nicotine dependence. Tobacco remains the largest cause of preventable mortality worldwide. CYP2A6, the primary hepatic nicotine metabolism gene, is robustly associated with cigarette consumption but other enzymes contribute to nicotine metabolism. We determined the effects of common variants in FMO3 on plasma levels of nicotine-N-oxide in 170 European Americans administered deuterated nicotine. The polymorphism rs2266780 (E308G) was associated with N-oxidation of both orally administered and ad libitum smoked nicotine (P⩽3.3 × 10-5 controlling for CYP2A6 genotype). In vitro, the FMO3 G308 variant was not associated with reduced activity, but rs2266780 was strongly associated with aberrant FMO3 mRNA splicing in both liver and brain (P⩽6.5 × 10-9). Surprisingly, in treatment-seeking European American smokers (n=1558) this allele was associated with reduced nicotine dependence, specifically with a longer time to first cigarette (P=9.0 × 10-4), but not with reduced cigarette consumption. As N-oxidation accounts for only a small percentage of hepatic nicotine metabolism we hypothesized that FMO3 genotype affects nicotine metabolism in the brain (unlike CYP2A6, FMO3 is expressed in human brain) or that nicotine-N-oxide itself has pharmacological activity. We demonstrate for the first time nicotine N-oxidation in human brain, mediated by FMO3 and FMO1, and show that nicotine-N-oxide modulates human α4β2 nicotinic receptor activity in vitro. These results indicate possible mechanisms for associations between FMO3 genotype and smoking behaviors, and suggest nicotine N-oxidation as a novel target to enhance smoking cessation.
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Affiliation(s)
- A M Teitelbaum
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - S E Murphy
- Department of Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - G Akk
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA.,Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - T B Baker
- Department of Psychology, University of Wisconsin, Madison, WI, USA
| | - A Germann
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA.,Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, MO, USA
| | - L B von Weymarn
- Department of Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - L J Bierut
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA
| | - A Goate
- Neuroscience Genetics & Genomics Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - E D Kharasch
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - A J Bloom
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA.,Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA
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7
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Zhou W, Humphries H, Neuhoff S, Gardner I, Masson E, Al-Huniti N, Zhou D. Development of a physiologically based pharmacokinetic model to predict the effects of flavin-containing monooxygenase 3 (FMO3) polymorphisms on itopride exposure. Biopharm Drug Dispos 2017; 38:389-393. [DOI: 10.1002/bdd.2074] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 01/27/2017] [Accepted: 02/28/2017] [Indexed: 12/13/2022]
Affiliation(s)
- Wangda Zhou
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham Massachusetts USA
| | | | | | | | - Eric Masson
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham Massachusetts USA
| | - Nidal Al-Huniti
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham Massachusetts USA
| | - Diansong Zhou
- Quantitative Clinical Pharmacology; AstraZeneca; Waltham Massachusetts USA
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8
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Effects of FMO3 Polymorphisms on Pharmacokinetics of Sulindac in Chinese Healthy Male Volunteers. BIOMED RESEARCH INTERNATIONAL 2017; 2017:4189678. [PMID: 28331852 PMCID: PMC5346382 DOI: 10.1155/2017/4189678] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 11/01/2016] [Accepted: 11/17/2016] [Indexed: 01/07/2023]
Abstract
Sulindac is a nonsteroidal anti-inflammatory drug, which is clinically used for the ailments of various inflammations. This study investigated the allele frequencies of FMO3 E158K and E308G and evaluated the influences of these two genetic polymorphisms on the pharmacokinetics of sulindac and its metabolites in Chinese healthy male volunteers. Eight FMO3 wild-type (FMO3 HHDD) subjects and seven FMO3 homozygotes E158K and E308G mutant (FMO3 hhdd) subjects were recruited from 247 healthy male volunteers genotyped by PCR-RFLP method. The plasma concentrations of sulindac, sulindac sulfide, and sulindac sulfone were determined by UPLC, while the pharmacokinetic parameters of the two different FMO3 genotypes were compared with each other. The frequencies of FMO3 E158K and E308G were 20.3% and 20.1%, respectively, which were in line with Hardy-Weinberg equilibrium (D′ = 0.977, r2 = 0.944). The mean values of Cmax, AUC0–24, and AUC0–∞ of sulindac were significantly higher in FMO3 hhdd group than those of FMO3 HHDD group (P < 0.05), while the pharmacokinetic parameters except Tmax of sulindac sulfide and sulindac sulfone showed no statistical difference between the two groups. The two FMO3 mutants were in close linkage disequilibrium and might play an important role in the pharmacokinetics of sulindac in Chinese healthy male volunteers.
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9
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Phillips IR, Shephard EA. Drug metabolism by flavin-containing monooxygenases of human and mouse. Expert Opin Drug Metab Toxicol 2016; 13:167-181. [PMID: 27678284 DOI: 10.1080/17425255.2017.1239718] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Flavin-containing monooxygenases (FMOs) play an important role in drug metabolism. Areas covered: We focus on the role of FMOs in the metabolism of drugs in human and mouse. We describe FMO genes and proteins of human and mouse; the catalytic mechanism of FMOs and their significance for drug metabolism; differences between FMOs and CYPs; factors contributing to potential underestimation of the contribution of FMOs to drug metabolism; the developmental and tissue-specific expression of FMO genes and differences between human and mouse; and factors that induce or inhibit FMOs. We discuss the contribution of FMOs of human and mouse to the metabolism of drugs and how genetic variation of FMOs affects drug metabolism. Finally, we discuss the utility of animal models for FMO-mediated drug metabolism in humans. Expert opinion: The contribution of FMOs to drug metabolism may be underestimated. As FMOs are not readily induced or inhibited and their reactions are generally detoxifications, the design of drugs that are metabolized predominantly by FMOs offers clinical advantages. Fmo1(-/-),Fmo2(-/-),Fmo4(-/-) mice provide a good animal model for FMO-mediated drug metabolism in humans. Identification of roles for FMO1 and FMO5 in endogenous metabolism has implications for drug therapy and initiates an exciting area of research.
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Affiliation(s)
- Ian R Phillips
- a Institute of Structural and Molecular Biology , University College London , London , UK.,b School of Biological and Chemical Sciences , Queen Mary University of London , London , UK
| | - Elizabeth A Shephard
- a Institute of Structural and Molecular Biology , University College London , London , UK
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10
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Zhou LP, Tan ZR, Chen H, Guo D, Chen Y, Huang WH, Wang LS, Zhang GG. Effect of two-linked mutations of the FMO3 gene on itopride metabolism in Chinese healthy volunteers. Eur J Clin Pharmacol 2014; 70:1333-8. [DOI: 10.1007/s00228-014-1724-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Accepted: 07/29/2014] [Indexed: 11/30/2022]
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Abstract
The pharmacokinetics of the atypical antipsychotic, olanzapine, display large interindividual variation leading to multiple-fold differences in drug exposure between patients at a given dose. This variation in turn gives rise to the need for individualized dosing in order to avoid concentration-dependent adverse effects or therapeutic failure. Genetically determined differences in olanzapine metabolism represent a less studied source of variability in comparison to environmental and physiological factors. In this review, we summarize available in vitro and in vivo data addressing the influence of polymorphisms in drug-metabolizing enzymes on olanzapine serum exposure. The polymorphic CYP2D6 enzyme appears to have no significant influence on olanzapine steady-state serum concentrations. The formation of the various olanzapine metabolites is influenced by polymorphisms in the genes coding for CYP1A2, CYP1A expression regulator AHR, UGT1A4 and UGT2B10, as well as FMO3. An impact on steady-state olanzapine serum concentrations has been suggested for variants of CYP1A2 and UGT1A4, with somewhat conflicting findings. The potential involvement of FMO1 and CYP3A43 in olanzapine disposition has also been suggested but needs future validation.
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Affiliation(s)
- Mao Mao Söderberg
- Department of Laboratory Medicine, Division of Clinical Pharmacology, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-14186 Stockholm, Sweden
| | - Marja-Liisa Dahl
- Department of Laboratory Medicine, Division of Clinical Pharmacology, Karolinska Institutet, Karolinska University Hospital Huddinge, SE-14186 Stockholm, Sweden.
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13
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Ozhan G, Topal P, Alpertunga B. Flavin-containing monooxygenase 3 gene polymorphisms in Turkish population. Toxicol Mech Methods 2012; 22:461-5. [PMID: 22409263 DOI: 10.3109/15376516.2012.672481] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Flavin-containing monooxygenases (FMOs) represent the second most important human monooxygenase system, after cytochrome P450s (CYPs) and catalyze the oxygenation of many chemicals containing nitrogen-, sulphur-, phosphorous-, selenium- and other nucleophilic heteroatoms. FMO3 is the prominent FMO form in adult human liver. For FMO3, both interindividual variability within a single ethnic group and variability between ethnic groups have been reported. In our study, three prevalent functional FMO3 variants (E158K, V257M, and E308G) were genotyped in healthy Turkish people by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) methods. The frequencies of alleles and haplotypes were compared with those obtained from different populations. It was found that FMO3 158K, 257M and 308G alleles, demonstrate impaired metabolism toward many FMO3 substrates, were observed frequently in Turkish population similar to the other populations. Also, the frequencies of haplotypes were determined based on individual allelic frequencies and it was observed that the most common haplotypes were haplotip EVE and KVE (E158K/V257M/E308G), which together accounted for 80% of all haplotypes. The obtained data from the present study could be useful for further studies assessing sensitivity to therapeutic drugs, environmental toxicants and common disease.
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Affiliation(s)
- Gül Ozhan
- Department of Pharmaceutical Toxicology, Faculty of Pharmacy, Istanbul University, Istanbul, Turkey
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14
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Catucci G, Gilardi G, Jeuken L, Sadeghi SJ. In vitro drug metabolism by C-terminally truncated human flavin-containing monooxygenase 3. Biochem Pharmacol 2012; 83:551-8. [DOI: 10.1016/j.bcp.2011.11.029] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2011] [Revised: 11/28/2011] [Accepted: 11/30/2011] [Indexed: 10/14/2022]
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15
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Shephard EA, Phillips IR. The potential of knockout mouse lines in defining the role of flavin-containing monooxygenases in drug metabolism. Expert Opin Drug Metab Toxicol 2010; 6:1083-94. [DOI: 10.1517/17425255.2010.503705] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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16
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Mao M, Matimba A, Scordo MG, Gunes A, Zengil H, Yasui-Furukori N, Masimirembwa C, Dahl ML. Flavin-containing monooxygenase 3 polymorphisms in 13 ethnic populations from Europe, East Asia and sub-Saharan Africa: frequency and linkage analysis. Pharmacogenomics 2009; 10:1447-55. [DOI: 10.2217/pgs.09.77] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aims: To investigate intra- and inter-ethnic differences in three widespread (E158K, V257M and E308G) and two African-specific (D132H and L360P) flavin-containing monooxygenase 3 (FMO3) polymorphisms. Materials & methods: Allele frequencies were determined by TaqMan® allelic discrimination assay in 2152 healthy volunteers from Europe (Swedes, Italians and Turks), East Asia (Japanese) and sub-Saharan Africa (nine ethnic groups covering eastern, southern and western regions), followed by haplotype and linkage analysis. Results: Significant subpopulation differences (p < 0.001) in allele frequencies were found for E158K, V257M and E308G in Europeans and regional differences (p < 0.01) for D132H among Africans. No carrier of P360 was identified. Cis-linkage between G308 and K158 was confirmed with the compound variant (K158/G308) being found in a high proportion (12.0–38.3%) of non-African subjects, but rarely (1.3%) among Africans. Conclusions: Distribution of functionally relevant FMO3 polymorphisms varies not only between ethnicities but also within. The K158/G308 variant may have potential clinical importance primarily in non-African populations due to its low prevalence in Africa.
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Affiliation(s)
- Mao Mao
- Department of Medical Sciences, Clinical Pharmacology, Uppsala University Hospital, Ent 61, SE-751 85 Uppsala, Sweden
| | - Alice Matimba
- IIDMM, University of Cape Town, South Africa
- African Institute of Biomedical Science and Technology, Harare, Zimbabwe
| | - Maria G Scordo
- Department of Medical Sciences, Clinical Pharmacology, Uppsala University Hospital, Ent 61, SE-751 85 Uppsala, Sweden
- University of Messina, Messina, Italy
| | - Arzu Gunes
- Department of Medical Sciences, Clinical Pharmacology, Uppsala University Hospital, Ent 61, SE-751 85 Uppsala, Sweden
- Gazi University, Ankara, Turkey
| | | | | | | | - Marja-Liisa Dahl
- Department of Medical Sciences, Clinical Pharmacology, Uppsala University Hospital, Ent 61, SE-751 85 Uppsala, Sweden
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Krueger SK, Vandyke JE, Williams DE, Hines RN. The Role of Flavin-Containing Monooxygenase (FMO) in the Metabolism of Tamoxifen and Other Tertiary Amines. Drug Metab Rev 2008; 38:139-47. [PMID: 16684653 DOI: 10.1080/03602530600569919] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Tamoxifen is utilized in breast cancer therapy and in chemoprevention. Tamoxifen may enhance risk for other neoplasias, especially endometrial cancer. The risk:benefit depends on the rate of metabolic activation versus detoxication. Cytochrome P450-dependent alpha-hydroxylation, followed by sulfonation, represents a metabolic activation pathway, producing products capable of covalent DNA adduction. In contrast, tamoxifen N-oxygenation represents a detoxication pathway, with the caveat that N-oxides can be reduced back to the parent amines. The N-oxygenation pathway will be the focus for this review. Dr. David Kupfer pioneered studies on cytochrome P450 and flavin-containing monooxygenase (FMO) tamoxifen metabolism. We collaborated with Dr. Kupfer's laboratory and recently determined that the low level of tamoxifen N-oxide production in human liver microsomes may be explained by the kinetics of FMO1 versus FMO3.
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Affiliation(s)
- Sharon K Krueger
- Department of Environmental and Molecular Toxicology, The Linus Pauling Institute, Oregon State University, Corvallis, 97331, USA
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Motika MS, Zhang J, Cashman JR. Flavin-containing monooxygenase 3 and human disease. Expert Opin Drug Metab Toxicol 2008; 3:831-45. [PMID: 18028028 DOI: 10.1517/17425255.3.6.831] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This review summarizes information concerning the association of the human flavin-containing monooxygenase 3 (FMO3) and human diseases. Human FMO3 oxygenates a wide variety of nucleophilic heteroatom-containing xenobiotics, including endogenous substrates and various clinically important drugs. In this article, the authors discuss the association of FMO3 with human disease, including: i) direct association of FMO3 genetic mutations to human genetic disease; ii) association of FMO3 genetic polymorphism to altered drug metabolism and, therefore, indirect association of FMO3 with drug therapeutic efficacy of human disease; and iii) the potential impact and/or effect of FMO3 transcriptional regulation during disease states. Even though many studies discussed for the latter two points are at a preliminary stage and require much more research to bring to a definite conclusion, the authors include these studies to stimulate general interest and invite further discussion.
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Affiliation(s)
- Meike S Motika
- Human Biomolecular Research Institute, 5310 Eastgate Mall, San Diego, CA 92121, USA
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19
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Hisamuddin IM, Yang VW. Genetic polymorphisms of human flavin-containing monooxygenase 3: implications for drug metabolism and clinical perspectives. Pharmacogenomics 2007; 8:635-43. [PMID: 17559352 PMCID: PMC2213907 DOI: 10.2217/14622416.8.6.635] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Flavin-containing monooxygenase 3 (FMO3) is a hepatic microsomal enzyme that oxidizes a host of drugs, xenobiotics and other chemicals. Numerous variants in the gene encoding FMO3 have been identified, some of which result in altered enzymatic activity and, consequently, altered substrate metabolism. Studies also implicate individual and ethnic differences in the frequency of FMO3 polymorphisms. In addition, new variants continue to be identified with potentially important clinical implications. For example, the role of FMO3 variants in the pathophysiology of gastrointestinal diseases is an evolving area of research. Two commonly occurring polymorphisms of FMO3, E158K and E308G, have been associated with a reduction in polyp burden in patients with familial adenomatous polyposis who were treated with sulindac sulfide, an FMO3 substrate. These findings suggest a potential role for prospective genotyping of common FMO3 polymorphisms in the treatment of disease states that involve the use of drugs metabolized by FMO3. This review summarizes the current state of research on the genetic polymorphisms of FMO3, with a focus on their clinical implications in gastrointestinal diseases.
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Affiliation(s)
- Irfan M Hisamuddin
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, 201 Whitehead Biomedical Research Building, 615 Michael Street, Atlanta, GA 30322, USA
| | - Vincent W Yang
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, 201 Whitehead Biomedical Research Building, 615 Michael Street, Atlanta, GA 30322, USA
- Winship Cancer Institute, Emory University School of Medicine, 201 Whitehead Biomedical Research Building, 615 Michael Street, Atlanta, GA 30322, USA, Tel.: +1 404 727 5638; Fax: +1 404 727 5767; E-mail:
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20
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Hao D, Sun J, Furnes B, Schlenk D, Li M, Yang S, Yang L. Allele and genotype frequencies of polymorphicFMO3 gene in two genetically distinct populations. Cell Biochem Funct 2007; 25:443-53. [PMID: 16598836 DOI: 10.1002/cbf.1326] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The aims of this study were to analyze flavin-containing monooxygenase 3 (FMO3) polymorphisms and allele and genotype frequencies in 256 Han Chinese and 50 African-American individuals, to compare the allele and genotype frequencies of these populations with those of other world populations. For Han Chinese, genotyping of three common single nucleotide polymorphisms, E158K, V257M and E308G was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). For African-Americans, genotyping of all coding exons was performed by modified PCR-single strand conformational polymorphism (SSCP). Evolutionary rates of FMO3 were estimated computationally. We found that there were significant differences in allele and genotype frequencies among Han Chinese, African-Americans and other world populations. In Han Chinese, the minor allele frequencies (MAFs) were 0.229 (E158K), 0.203 (V257M) and 0.148 (E308G), respectively. In African-Americans, MAFs were 0.48 (E158K), 0.05 (V257M) and 0 (E308G), respectively. There was rapid evolution during the divergence of primate FMO3. This is the first report comparing FMO alleles and genotypes between Han Chinese and African-Americans. A Han Chinese population database has been established for three gene polymorphisms. The data presented here justify further pharmacogenetic studies for potentially optimizing recommended drug dosages and evaluating relationships with disease processes.
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Affiliation(s)
- DaCheng Hao
- Laboratory of Pharmaceutical Resource Discovery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
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21
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Hao DC, Sun J, Furnes B, Schlenk D, Hou ZF, Zhang YP, Yang SL, Yang L. Haplotype Frequency Distribution and Linkage Disequilibrium Analysis of Single Nucleotide Polymorphisms at the Human FMO3 Gene Locus. Biochem Genet 2006; 44:391-407. [PMID: 17096187 DOI: 10.1007/s10528-006-9037-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2005] [Accepted: 01/04/2006] [Indexed: 10/23/2022]
Abstract
We analyzed flavin-containing monooxygenase 3 (FMO3) polymorphisms, haplotype structure, and linkage disequilibrium (LD) in 256 Han Chinese and 50 African-American individuals to compare their haplotype frequencies and LD with other world populations. For the Han Chinese, genotyping of three haplotype tag single nucleotide polymorphisms (E158K, V257M, and E308G) was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism. For the African-Americans, genotyping of all coding exons was performed by modified PCR-single strand conformational polymorphism. Haplotype frequencies, LD, and evolutionary rates were inferred and estimated computationally. There were significant differences in haplotype frequency distribution and LD pattern among Han Chinese, African-Americans, and other world populations. Four major haplotypes of Han Chinese were EVE, KVE, EME, and EVG. Two major haplotypes of African-Americans were EVE and KVE. We found that sites 158 and 257 are in significant LD in both populations. This is the first report comparing FMO haplotypes and LD of Han Chinese with African-Americans. The data presented here justify further pharmacogenetic studies for potentially optimizing recommended drug dosages and evaluating relationships with disease processes.
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Affiliation(s)
- Da-Cheng Hao
- Laboratory of Pharmaceutical Resource Discovery, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
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Borbás T, Zhang J, Cerny MA, Likó I, Cashman JR. Investigation of structure and function of a catalytically efficient variant of the human flavin-containing monooxygenase form 3. Drug Metab Dispos 2006; 34:1995-2002. [PMID: 16985102 DOI: 10.1124/dmd.106.010827] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To characterize the contribution of amino acid 360 to the functional activity of the human flavin-containing monooxygenase form 3 (FMO3) and form 1 (FMO1) in the oxygenation of drugs and chemicals, we expressed four FMO3 variants (i.e., Ala360-FMO3, His360-FMO3, Gln360-FMO3, and Pro360-FMO3) and one FMO1 variant (i.e., Pro360-FMO1) and compared them to wild-type enzymes (Leu360-FMO3 and His360-FMO1, respectively). The amino acid substitutions were introduced into wild-type FMO3 or FMO1 cDNA by site-directed mutagenesis. The thermal stability of variants of Leu360 FMO3 was also studied, and the thermal stability was significantly different from that of wild-type FMO3. The influence of different substrates to modulate the catalytic activity of FMO3 variants was also examined. Selective functional substrate activity was determined with mercaptoimidazole, chlorpromazine, and 10-[(N,N-dimethylaminopentyl)-2-(trifluoromethyl)]phenothiazine. Compared with wild-type FMO3, the Ala360-FMO3 and His360-FMO3 variants were less catalytically efficient for mercaptoimidazole S-oxygenation. N-Oxygenation of chlorpromazine was significantly less catalytically efficient for His360-FMO3 compared with wild-type FMO3. Human Pro360-FMO1 was significantly more catalytically efficient at S-oxygenating mercaptoimidazole and chlorpromazine compared with wild-type FMO1. The data support the mechanism that the Pro360 loci affect thermal stability of FMO3. Because different amino acids at position 360 affect substrate oxygenation in a unique fashion compared with that of FMO3 stimulation, we conclude that the mechanism of stimulation of FMO3 is distinct from that of enzyme catalysis. A molecular model of human FMO3 was also constructed to help explain the results. The increase in catalytic efficiency observed for Pro360 in human FMO3 was also observed when the His of FMO1 was replaced by Pro at loci 360.
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Affiliation(s)
- Tímea Borbás
- Human BioMolecular Research Institute, San Diego, CA 92121, USA
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Bae SY, Choi SK, Kim KR, Park CS, Lee SK, Roh HK, Shin DW, Pie JE, Woo ZH, Kang JH. Effects of genetic polymorphisms of MDR1, FMO3 and CYP1A2 on susceptibility to colorectal cancer in Koreans. Cancer Sci 2006; 97:774-9. [PMID: 16800822 DOI: 10.1111/j.1349-7006.2006.00241.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The aim of the present study was to evaluate the effects on the susceptibility to colorectal cancer (CRC) of genetic polymorphisms in P-glycoprotein (PGP) and the metabolic enzymes cytochrome P450 1A2 (CYP1A2) and flavin-containing monooxygenase 3 (FMO3). We analyzed five single-nucleotide polymorphisms (SNP) in 93 cancer-free volunteers and 111 patients with CRC: one common genetic variant of the PGP-encoding MDR1 gene and four SNP in genes for metabolic enzymes (two SNP in FMO3 and two SNP in CYP1A2). The genotypes and allele frequencies of the MDR1/C3435T, FMO3/G488A, FMO3/A923G and CYP1A2/G-3860 A polymorphisms were not significantly different in cancer-free subjects and CRC patients. However, a significant association was found between the CYP1A2/A-163C polymorphism and the risk of CRC, particularly in elderly (>55 years) subjects and smokers. A phenotyping study in normal smokers showed that the CYP1A2 activity of subjects with the CYP1A2/-163 AA genotype was significantly lower than that of subjects carrying the CYP1A2/-163C allele. Combined results show that the CYP1A2/-163C allele is significantly associated with an increase in CYP1A2 activity and a consequent increased risk of CRC in Koreans, particularly in elderly people and smokers.
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Affiliation(s)
- Sun-Young Bae
- Department of Surgery, Inha Institute of Research for Medical Sciences, College of Medicine, Inha University, Incheon 410-712, Korea
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Abstract
This review summarizes recent information concerning the pharmacological and toxicological significance of the human flavin-containing monooxygenase (FMO, EC 1.14.13.8). The human FMO oxygenates nucleophilic heteroatom-containing chemicals and drugs and generally converts them into harmless, polar, readily excreted metabolites. Sometimes, however, FMO bioactivates chemicals into reactive materials that can cause toxicity. Most of the interindividual differences of FMO are due to genetic variability and allelic variation, and splicing variants may contribute to interindividual and interethnic variability observed for FMO-mediated metabolism. In contrast to cytochrome P450 (CYP), FMO is not easily induced nor readily inhibited, and potential adverse drug-drug interactions are minimized for drugs prominently metabolized by FMO. These properties may provide advantages in drug design and discovery, and by incorporating FMO detoxication pathways into drug candidates, more drug-like materials may be forthcoming. Although exhaustive examples are not available, physiological factors can influence FMO function, and this may have implications for the clinical significance of FMO and a role in human disease.
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Affiliation(s)
- John R Cashman
- Human BioMolecular Research Institute, San Diego, CA 92121, USA.
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Hukkanen J, Dempsey D, Jacob P, Benowitz NL. Effect of pregnancy on a measure of FMO3 activity. Br J Clin Pharmacol 2006; 60:224-6. [PMID: 16042678 PMCID: PMC1884929 DOI: 10.1111/j.1365-2125.2005.02406.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Koukouritaki SB, Hines RN. Flavin-containing monooxygenase genetic polymorphism: impact on chemical metabolism and drug development. Pharmacogenomics 2005; 6:807-22. [PMID: 16296944 DOI: 10.2217/14622416.6.8.807] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The flavin-containing monooxygenases (FMOs) metabolize a broad range of therapeutics. Consisting of five gene products in humans (FMO1–5), the different FMO family members exhibit pronounced tissue- and temporal-specific expression patterns. Substantial interindividual differences are also observed, and the inability to modulate with exogenous agents is consistent with an important role for genetic variation. Several rare FMO3 alleles causative for trimethylaminuria have been well characterized. However, the identification and characterization of functional FMO1–5 polymorphisms has been more recent. Although none of these polymorphisms has been associated with an adverse drug reaction, the continued broadening of our therapeutic armamentarium makes such an event likely in the future. Furthermore, at least one example has been reported for a direct association between FMO3 polymorphism and therapeutic efficacy. Thus, it is anticipated that knowledge regarding functionally-relevant FMO genetic variability will become increasingly important for making drug development and patient therapeutic choices.
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Affiliation(s)
- Sevasti B Koukouritaki
- Medical College of Wisconsin, Department of Pediatrics, Clinical Pharmacology, Pharmacogenetics and Teratology Section, 8701 Watertown Plank Rd., Milwaukee, Wisconsin 53226, USA
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Cashman JR. Some distinctions between flavin-containing and cytochrome P450 monooxygenases. Biochem Biophys Res Commun 2005; 338:599-604. [PMID: 16112078 DOI: 10.1016/j.bbrc.2005.08.009] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Accepted: 08/04/2005] [Indexed: 11/27/2022]
Abstract
This minireview summarizes information concerning the differences and similarities of the human flavin-containing- (FMO, E.C. 1.14.13.8) and the cytochrome P450-monooxygenases (CYP, E.C. 1.14.14.1). Human FMO oxygenates soft nucleophiles. CYP mainly catalyzes C-H abstraction but also oxidizes nitrogen- and sulfur-containing compounds. Both FMO and CYP generally convert lipophilic compounds into more hydrophilic metabolites. The mechanism by which each monooxygenase operates is quite distinct. Sometimes, CYP or FMO bioactivate chemicals to reactive metabolites but to date, drug toxicity thus far observed in the clinic is mainly the result of CYP-dependent oxidation. Both FMO and CYP possess genetic variability that may contribute to inter-individual variability observed for drug metabolism. In contrast to CYP, FMO is not induced or readily inhibited and potential adverse drug-drug interactions are minimized for drugs prominently metabolized by FMO. These properties may provide advantages in drug design, and by incorporating FMO detoxication pathways into drug candidates, more drug-like materials may emerge.
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Affiliation(s)
- John R Cashman
- Human BioMolecular Research Institute, 5310 Eastgate Mall, San Diego, CA 92121, USA.
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Krueger SK, Williams DE. Mammalian flavin-containing monooxygenases: structure/function, genetic polymorphisms and role in drug metabolism. Pharmacol Ther 2005; 106:357-87. [PMID: 15922018 PMCID: PMC1828602 DOI: 10.1016/j.pharmthera.2005.01.001] [Citation(s) in RCA: 395] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/03/2005] [Indexed: 10/25/2022]
Abstract
Flavin-containing monooxygenase (FMO) oxygenates drugs and xenobiotics containing a "soft-nucleophile", usually nitrogen or sulfur. FMO, like cytochrome P450 (CYP), is a monooxygenase, utilizing the reducing equivalents of NADPH to reduce 1 atom of molecular oxygen to water, while the other atom is used to oxidize the substrate. FMO and CYP also exhibit similar tissue and cellular location, molecular weight, substrate specificity, and exist as multiple enzymes under developmental control. The human FMO functional gene family is much smaller (5 families each with a single member) than CYP. FMO does not require a reductase to transfer electrons from NADPH and the catalytic cycle of the 2 monooxygenases is strikingly different. Another distinction is the lack of induction of FMOs by xenobiotics. In general, CYP is the major contributor to oxidative xenobiotic metabolism. However, FMO activity may be of significance in a number of cases and should not be overlooked. FMO and CYP have overlapping substrate specificities, but often yield distinct metabolites with potentially significant toxicological/pharmacological consequences. The physiological function(s) of FMO are poorly understood. Three of the 5 expressed human FMO genes, FMO1, FMO2 and FMO3, exhibit genetic polymorphisms. The most studied of these is FMO3 (adult human liver) in which mutant alleles contribute to the disease known as trimethylaminuria. The consequences of these FMO genetic polymorphisms in drug metabolism and human health are areas of research requiring further exploration.
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Key Words
- flavin monooxygenase
- drug metabolism
- fmo
- bvmos, baeyer–villiger monooxygenases
- cyp, cytochrome p450
- dbm, dinucleotide-binding motif
- fadpnr, fad-dependent pyridine nucleotide reductase prints signature
- fmo, flavin-containing monooxygenase
- fmoxygenase, fmo prints signature
- gr, glutathione reductase
- pamo, phenylacetone monooxygenase
- pndrdtasei, pyridine nucleotide disulfide reductase class-i prints signature
- ros, reactive oxygen species
- snp, single-nucleotide polymorphism
- tmau, trimethylaminuria
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Affiliation(s)
- Sharon K. Krueger
- Department of Environmental and Molecular Toxicology and The Linus Pauling Institute, Oregon State University, United States
| | - David E. Williams
- Department of Environmental and Molecular Toxicology and The Linus Pauling Institute, Oregon State University, United States
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Blake MJ, Castro L, Leeder JS, Kearns GL. Ontogeny of drug metabolizing enzymes in the neonate. Semin Fetal Neonatal Med 2005; 10:123-38. [PMID: 15701578 DOI: 10.1016/j.siny.2004.11.001] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Fetal exposure to xenobiotics is modulated to a considerable degree by the metabolic capabilities of the mother and the placenta. However, once liberated from the uterine environment the neonate is instantly exposed to a wide array of new macromolecules in the form of byproducts of cellular metabolism, dietary constituents, environmental toxins and pharmacologic agents. The rapid and efficient biotransformation of these compounds by Phase I and Phase II drug-metabolizing enzymes is an essential process if the infant is to avoid the accumulation of reactive compounds that could produce cellular injury or tissue dysfunction. Genetic polymorphisms and environmental factors are known to contribute dramatically to individual variation in the activity of drug-metabolizing enzymes. More recently, it has become apparent that programmed, developmental, regulatory events occur - independent of genotype - which further add to individual variation in drug metabolism. An appreciation of the impact of ontogeny on the expression and functional activity of the major drug-metabolizing enzymes enables the practicing clinician to predict the ultimate consequence of drug administration in the neonate to help guide optimal drug therapy.
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Affiliation(s)
- Michael J Blake
- Department of Pediatrics, University of Missouri - Kansas City, Division of Pediatric Pharmacology and Medical Toxicology, The Children's Mercy Hospitals and Clinics, 2401 Gillham Road, Kansas City, MO 64108, USA
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Ryu SD, Kang JH, Yi HG, Nahm CH, Park CS. Hepatic flavin-containing monooxygenase activity attenuated by cGMP-independent nitric oxide-mediated mRNA destabilization. Biochem Biophys Res Commun 2004; 324:409-16. [PMID: 15465034 DOI: 10.1016/j.bbrc.2004.09.065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Indexed: 10/26/2022]
Abstract
To identify the novel mechanism by which nitric oxide (NO) suppresses flavin-containing monooxygenase (FMO) activity in endotoxemic rat livers, NO-overproducing conditions were induced in primary cultured rat hepatocytes by treatment with a mixture (LCM) of lipopolysaccharide and proinflammatory cytokines (IL-1beta, TNF-alpha, and IFN-gamma), or by the addition of a pure NO donor, spermine-NONOate. mRNA levels of the major hepatic form, FMO1, decreased via a cGMP-independent destabilizing effect of NO rather than by decreased transcription. The decrease in the mRNA levels caused by LCM-induced inducible NO synthase (iNOS) was completely blocked by co-treatment with aminoguanidine, a selective iNOS inhibitor. Furthermore, spermine-NONOate, but not the cGMP analog, 8-bromo-cGMP, dose- and time-dependently attenuated FMO1 mRNA stability in actinomycin-D-pretreated cells, resulting in decreases in protein levels and biochemical activity. These results suggest that NO acts directly in a cGMP-independent mechanism by decreasing the half-life of FMO1 mRNA, thereby inducing impairment of FMO-related functions in endotoxemia.
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Affiliation(s)
- Seung-Duk Ryu
- Department of Pharmacology and Toxicology, College of Medicine, Medicinal Toxicology Research Center, CDIR, Inha University, Incheon 400-103, Republic of Korea
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Ryu SD, Yi HG, Cha YN, Kang JH, Kang JS, Jeon YC, Park HK, Yu TM, Lee JN, Park CS. Flavin-containing monooxygenase activity can be inhibited by nitric oxide-mediated S-nitrosylation. Life Sci 2004; 75:2559-72. [PMID: 15363661 DOI: 10.1016/j.lfs.2004.05.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2004] [Accepted: 05/13/2004] [Indexed: 10/26/2022]
Abstract
Nitric oxide (NO) modifies the functions of a variety of proteins containing cysteine thiols or transition-metal centers, particularly by S-nitrosylation. In inflamed liver, NO is overproduced and hepatic drug-metabolizing enzymes, the flavin-containing monooxygenases (FMOs) and cytochrome P450s (CYPs), are suppressed. However, the NO-related mechanisms underlying the loss of these activities are not well understood, particularly for FMOs. In this study, we suggest that FMO3, the major FMO in human liver, is modified post-translationally by NO. This hypothesis is based on the imbalance observed between the decrease in FMO3 expression (40.7% of controls) and FMO3-specific ranitidine N-oxidation activity (15.1%), and on the partial or complete reversibility of FMO inhibition by sulfhydryl-reducing regents such as DTT (effective on both S-S and S-NO adducts) and ascorbate (effective on S-NO only). Furthermore, NO donors (SNP, SNAP, and Sin-1), including the pure NO donor DEA/NO, directly suppressed in vitro FMO activity (N- or S-oxidation of ranitidine, trimethylamine, and thiobenzamide) in human liver microsomal proteins and recombinant human FMO3. These activities were restored completely after treatment with DTT or ascorbate. These results suggest that NO-mediated S-nitrosylation is involved in the rigorous inhibition of FMO activity in vitro and in vivo, resulting in the suppression of FMO-based drug metabolism or detoxification.
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Affiliation(s)
- Seung-Duk Ryu
- Department of Pharmacology, Medicinal Toxicology Research Center, College of Medicine, Inha University, Incheon 400-103, South Korea
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Lattard V, Zhang J, Tran Q, Furnes B, Schlenk D, Cashman JR. Two new polymorphisms of the FMO3 gene in Caucasian and African-American populations: comparative genetic and functional studies. Drug Metab Dispos 2003; 31:854-60. [PMID: 12814961 DOI: 10.1124/dmd.31.7.854] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To characterize the contribution of the human flavin-containing monooxygenase form 3 (FMO3) in the metabolism and disposition of drugs and xenobiotics, we determined the single nucleotide polymorphisms in the coding region and adjacent splice junctions of FMO3 in 134 African Americans and 120 Caucasians from the United States. In the regions examined, DNA resequencing or high throughput MassEXTEND studies coupled with mass spectrometric genotyping showed that 12 sites of variation were present. Three variants encoding synonymous mutations and four polymorphisms were observed in the noncoding region. Another three variants, Lys158-FMO3, Met257-FMO3 and Gly308-FMO3, previously reported in similar populations, were prominent polymorphisms. Two new polymorphisms, His132-FMO3 and Pro360-FMO3, were identified in this study. Both variants were found only in African Americans. To evaluate the effect of the amino acid substitutions on the function of FMO3, each amino acid substitution was introduced by site-directed mutagenesis into a wild-type FMO3 cDNA. Selective functional activity was studied with methimazole, trimethylamine, and 10-(N,N-dimethylaminopentyl)-2-(trifluoromethyl) phenothiazine. Both His132-FMO3 and Pro360-FMO3 variants were able to metabolize the substrates examined. Compared with wild-type FMO3, the His132-FMO3 was less catalytically efficient. The His132-FMO3 variant moderately altered the catalytic efficiency of FMO3 (decrease of 30%, 60% and 6% with methimazole, trimethylamine and 10-(N,N-dimethylaminopentyl)-2-(trifluoromethyl)phenothiazine, respectively). The Pro360-FMO3 variant was more catalytically efficient than wild-type FMO3. Pro360-FMO3 oxygenated methimazole, trimethylamine and 10-(N,N-dimethylaminopentyl)-2-(trifluoromethyl)phenothiazine, respectively, 3-, 5- and 2-fold more efficiently than wild-type FMO3. Based on the functional activity of the variant FMO3 enzymes, it is likely that population differences exist for compounds primarily metabolized by FMO3.
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Affiliation(s)
- Virginie Lattard
- Human BioMolecular Research Institute, 5310 Eastgate Mall, San Diego, CA 92121, USA
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Shader RI, Greenblatt DJ. The safety of over-the-counter drugs: some reflections and unanswered questions. J Clin Psychopharmacol 2003; 23:111-2. [PMID: 12640210 DOI: 10.1097/00004714-200304000-00001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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34
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Cashman JR, Zhang J. Interindividual differences of human flavin-containing monooxygenase 3: genetic polymorphisms and functional variation. Drug Metab Dispos 2002; 30:1043-52. [PMID: 12228178 DOI: 10.1124/dmd.30.10.1043] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The human flavin-containing monooxygenase (form 3) (FMO3) participates in the oxygenation of nucleophilic heteroatom-containing drugs, xenobiotics, and endogenous materials. Currently, six forms of the FMO gene are known, but it is FMO3 that is the major form in adult human liver that is likely responsible for the majority of FMO-mediated metabolism. The substrate structural feature requirements for human FMO3 is beginning to become known to a greater extent and a few chemicals extensively metabolized by FMO3 have been reported. Expression of FMO3 is species- and tissue-specific, but unlike human cytochrome p450, mammalian FMO3 does not appear to be inducible. Interindividual variation in FMO3-dependent metabolism of drugs, chemicals, and endogenous material is therefore more likely due to genetic effects and not environmental ones. Examples of such interindividual variation come from the study of very rare mutations of the human FMO3 gene that have been associated with deficient N-oxygenation of dietary trimethylamine. Defective trimethylamine N-oxygenation causes trimethylaminuria or "fish-like odor syndrome". Information on human FMO3 mutations from individuals suffering from the condition of trimethylaminuria has provided knowledge about the underlying molecular mechanism(s) for trimethylaminuria. A number of common variants of human FMO3 have been reported. Diversification of the FMO3 gene may have led to selective advantages and new functions. As more examples of human FMO3-mediated metabolism of drugs or new chemical entities are discovered in the future, it is possible that FMO3 allelic variation may be shown to contribute to interindividual and interethnic variability of FMO-mediated metabolism. Human FMO3 may be another example of an environmental gene that participates in a protective mechanism to help humans ward off potentially toxic exposure of chemicals.
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Affiliation(s)
- John R Cashman
- Human BioMolecular Research Institute, San Diego 92121, California.
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Cashman JR. Human flavin-containing monooxygenase (form 3): polymorphisms and variations in chemical metabolism. Pharmacogenomics 2002; 3:325-39. [PMID: 12052141 DOI: 10.1517/14622416.3.3.325] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The human flavin-containing monooxygenases catalyze the oxygenation of nucleophilic heteroatom-containing drugs, xenobiotics and endogenous materials. Evidence for six forms of the FMO gene exist but it is FMO form 3 (FMO3) that is the prominent form in adult human liver that is likely to be associated with the bulk of FMO-mediated metabolism. An understanding of the substrate specificity of human FMO3 is beginning to emerge and several examples of drugs and chemicals extensively metabolized by FMO3 have been reported. Expression of FMO3 is species- and tissue-specific, but unlike human cytochrome P450 (CYP450), mammalian FMO3 does not appear to be inducible. Interindividual variation in FMO3-dependent metabolism of drugs, chemicals and endogenous materials is therefore more likely to be due to genetic and not environmental effects. Certain mutations of the human FMO3 gene have been associated with abnormal N-oxygenation of trimethylamine. Deficient N-oxygenation of trimethylamine results in a condition called trimethylaminuria. Some treatment strategies for this inborn error of metabolism are discussed. Other common variants of the FMO3 gene including E158K, V257M and E308G have been observed. It is possible that allelic variation of human FMO3 causes abnormal metabolism of chemicals and has clinical implications for human drug metabolism, but this is an understudied area. Human FMO3 allelic variation may eventually be shown to contribute to interindividual and interethnic variability in FMO3-mediated metabolism. Human FMO3 may be another example of an environmental gene that participates in a protective mechanism to help shield humans from potentially toxic exposure to chemicals. Heterogeneity in the relative frequencies of single and multiple site alleles, haplotypes and genotypes of the human FMO3 amongst various ethnic groups suggests population differences.
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Affiliation(s)
- John R Cashman
- Human BioMolecular Research Institute, 5310 Eastgate Mall, San Diego, CA 92121, USA.
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Koukouritaki SB, Simpson P, Yeung CK, Rettie AE, Hines RN. Human hepatic flavin-containing monooxygenases 1 (FMO1) and 3 (FMO3) developmental expression. Pediatr Res 2002; 51:236-43. [PMID: 11809920 DOI: 10.1203/00006450-200202000-00018] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The flavin-containing monooxygenases (FMOs) are important for the metabolism of numerous therapeutics and toxicants. Six mammalian FMO genes (FMO1-6) have been identified, each exhibiting developmental and tissue- and species-specific expression patterns. Previous studies demonstrated that human hepatic FMO1 is restricted to the fetus whereas FMO3 is the major adult isoform. These studies failed to describe temporal expression patterns, the precise timing of the FMO1/FMO3 switch, or potential control mechanisms. To address these questions, FMO1 and FMO3 were quantified in microsomal fractions from 240 human liver samples representing ages from 8 wk gestation to 18 y using Western blotting. FMO1 expression was highest in the embryo (8-15 wk gestation; 7.8 +/- 5.3 pmol/mg protein). Low levels of FMO3 expression also were detectable in the embryo, but not in the fetus. FMO1 suppression occurred within 3 d postpartum in a process tightly coupled to birth, but not gestational age. The onset of FMO3 expression was highly variable, with most individuals failing to express this isoform during the neonatal period. FMO3 was detectable in most individuals by 1-2 y of age and was expressed at intermediate levels until 11 y (12.7 +/- 8.0 pmol/mg protein). These data suggest that birth is necessary, but not sufficient for the onset of FMO3 expression. A gender-independent increase in FMO3 expression was observed from 11 to 18 y of age (26.9 +/- 8.6 pmol/mg protein). Finally, 2- to 20-fold interindividual variation in FMO1 and FMO3 protein levels were observed, depending on the age bracket.
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Affiliation(s)
- Sevasti B Koukouritaki
- Department of Pediatrics, Birth Defects Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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Park CS, Kang JH, Chung WG, Yi HG, Pie JE, Park DK, Hines RN, McCarver DG, Cha YN. Ethnic differences in allelic frequency of two flavin-containing monooxygenase 3 (FMO3) polymorphisms: linkage and effects on in vivo and in vitro FMO activities. PHARMACOGENETICS 2002; 12:77-80. [PMID: 11773868 DOI: 10.1097/00008571-200201000-00011] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- Chang-Shin Park
- Department of Pharmacology and Toxicology, Nitric Oxide Radical Toxicology Research Center, College of Medicine, Inha University, Inchon, Korea
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Kubota M, Nakamoto Y, Nakayama K, Ujjin P, Satarug S, Mushiroda T, Yokoi T, Funayama M, Kamataki T. A Mutation in the Flavin-containing Monooxygenase 3 Gene and its Effects on Catalytic Activity for N-oxidation of Trimethylamine In Vitro. Drug Metab Pharmacokinet 2002; 17:207-13. [PMID: 15618671 DOI: 10.2133/dmpk.17.207] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To clarify the mutation of the flavin-containing monooxygenase (FMO) 3 gene causing fish-odor syndrome, we analyzed the FMO3 gene of a Thai subject who possibly suffered from fish-odor syndrome. A novel mutation, a single-base substitution from G to A at the position of 265 (G265A), was identified in exon 3. The mutation caused an amino acid substitution from valine to isoleucine at residue 58 (V58I). The mutated FMO3 protein with V58I exhibited the reduced trimethylamine N-oxidase activity when it was expressed in E. coli. The V(max)/K(m) value for the activity of the mutant-type FMO3 was about 5 times lower than that for the wild-type FMO3.
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Affiliation(s)
- Megumi Kubota
- Laboratory of Drug Metabolism, Division of Pharmacobio-dynamics, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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Lambert DM, Mamer OA, Akerman BR, Choinière L, Gaudet D, Hamet P, Treacy EP. In vivo variability of TMA oxidation is partially mediated by polymorphisms of the FMO3 gene. Mol Genet Metab 2001; 73:224-9. [PMID: 11461189 DOI: 10.1006/mgme.2001.3189] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Trimethylaminuria (TMAU) results from an accumulation of an excessive amount of unoxidized trimethylamine that is excreted in urine and body secretions. Mutations of the flavin-containing monooxygenase 3 (FMO3) gene (a hepatic phase I drug-metabolizing enzyme) account for the severe recessively encoded form of this condition. We have previously described a number of FMO3 polymorphisms which in vitro exhibit reduced substrate affinity for several FMO substrates. Here we show that three prevalent polymorphisms (E158K, V257M, and E308G) inherited in particular combinations confer a slight decrease in TMA oxidation under normal physiological conditions, which may be clinically "silent." With the use of substrate loading or with the interaction of other known modulators of FMO3 activity such as hormonal influences, these genotypes may predispose to mild TMAU.
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Affiliation(s)
- D M Lambert
- Biochemical Genetics, Montreal Children's Hospital, Montreal, Quebec, Canada
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Hoskins J, Shenfield G, Murray M, Gross A. Characterization of moclobemide N-oxidation in human liver microsomes. Xenobiotica 2001; 31:387-97. [PMID: 11531003 DOI: 10.1080/00498250110055488] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
1. Moclobemide underdergoes morpholine ring N-oxidation to form a major metabolite in plasma Rol2-5637. 2. The kinetics of moclobemide N-oxidation in human liver microsomes (HLM) (n = 6) have been investigated and the mixed-function oxidase enzymes catalysing this reaction have been identified using inhibition, enzyme correlation, altered pH and heat pretreatment experiments. 3. N-oxidation followed single enzyme Michealis-Menten kinetics (0.02-4.0 mm). Km app and Vmax ranged from 0.48 to 1.35 mM (mean +/- SD) 0.77 +/- 0.34 mM) and 0.22 to 2.15 nmol mg(-1) min(-1) (1.39 +/- 0.80 nmol mg(-1) respectively. 4. The N-oxidation of moclobemide strongly correlated with benzydamine N-oxidation a probe reaction for flavin-containing monoxygenase (FMO) activity (0.1 mM moclobemide, rs = 0.81, p < 0.005; 4 mM moclobemide, rs = 0.94, p = 0.0001). Correlations were observed between moclobemide N-oxidation and specific cytochromre P450 (CYP) activities at both moclobemide concentrations (0.1 mM moclobemide, CYP2C19 0.66, p < 0.05; 4 mM moclobemide, CYP2E1 rs = 0.56, p < 0.05). 5. The general P450 inhibitor, N-benzylimidazole, did not affect the rate of Rol2-5637 formation (0% inhibition versus control) (at 1.3 mM moclobemide. Furthermore, the rate of Ro12-5637 formation in HLM was unaffected by inhibitors Or substrates of specific P450s (< 10% inhibition versus control). 6. Heat pretreatment of HLM in the absence of NADPH (inactivating FMOs) resulted in 97% inhibition of Ro12-5637 formation. N-oxidation activity was greatest when incubated at pH 8.5. These results ilre consistent with the reaction being FMO medialtetd . 7. In conclusion, moclobemide N-oxidation activity has been observed in HLM in vitro and the reaction is predominantly catalysed by FMOs with a potentially small contribution from cytochrome P450 isoforms.
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Affiliation(s)
- J Hoskins
- Department of Clinical Pharmacology, Royal North Shore Hospital, St Leonards, NSW, Australia.
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Chung WG, Park CS, Roh HK, Lee WK, Cha YN. Oxidation of ranitidine by isozymes of flavin-containing monooxygenase and cytochrome P450. JAPANESE JOURNAL OF PHARMACOLOGY 2000; 84:213-20. [PMID: 11128045 DOI: 10.1254/jjp.84.213] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Rat and human liver microsomes oxidized ranitidine to its N-oxide (66-76%) and S-oxide (13-18%) and desmethylranitidine (12-16%). N- and S-oxidations of ranitidine were inhibited by metimazole [flavin-containing monooxygenase (FMO) inhibitor] to 96-97% and 71-85%, respectively, and desmethylation of ranitidine was inhibited by SKF525A [cytochrome P450 (CYP) inhibitor] by 71-95%. Recombinant FMO isozymes like FMO1, FMO2, FMO3 and FMO5 produced 39, 79, 2180 and 4 ranitinine N-oxide and 45, 0, 580 and 280 ranitinine S-oxide pmol x min(-1) x nmol(-1) FMO, respectively. Desmethyranitinine was not produced by recombinant FMOs. Production of desmethylranitidine by rat and human liver microsomes was inhibited by tranylcypromine, a-naphthoflavon and quinidine, which are known to inhibit CYP2C19, 1A2 and 2D6, repectively. FMO3, the major form in adult liver, produced both ranitidine N- and S-oxides at a 4 to 1 ratio. FMO1, expressed primarily in human kidney, was 55- and 13-fold less efficient than the hepatic FMO3 in producing ranitidine N- and S-oxides, respectively. FMO2 and FMO5, although expressed slightly in human liver, kidney and lung, were not efficient producers of ranitidine N- and S-oxides. Thus, urinary contents of ranitidine N-oxide can be used as the in vivo probe to determine the hepatic FMO3 activity.
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Affiliation(s)
- W G Chung
- Department of Pharmacology and Medicinal Toxicology Research Center, Inha University, Inchon, Korea
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