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Human cytochrome P450 enzymes bind drugs and other substrates mainly through conformational-selection modes.
Guengerich FP, Wilkey CJ, Phan TTN
(2019) J Biol Chem 294: 10928-10941
MeSH Terms: Catalysis, Cytochrome P-450 CYP2D6, Cytochrome P-450 CYP2E1, Cytochrome P-450 CYP3A, Cytochrome P-450 Enzyme Inhibitors, Cytochrome P-450 Enzyme System, Humans, Kinetics, Lauric Acids, Ligands, Molecular Conformation, Oxidation-Reduction, Palmitic Acid, Protein Binding, Protein Conformation, Spiro Compounds, Substrate Specificity
Show Abstract · Added March 3, 2020
Cytochrome P450 (P450) enzymes are major catalysts involved in the oxidations of most drugs, steroids, carcinogens, fat-soluble vitamins, and natural products. The binding of substrates to some of the 57 human P450s and other mammalian P450s is more complex than a two-state system and has been proposed to involve mechanisms such as multiple ligand occupancy, induced-fit, and conformational-selection. Here, we used kinetic analysis of binding with multiple concentrations of substrates and computational modeling of these data to discern possible binding modes of several human P450s. We observed that P450 2D6 binds its ligand rolapitant in a mechanism involving conformational-selection. P450 4A11 bound the substrate lauric acid via conformational-selection, as did P450 2C8 with palmitic acid. Binding of the steroid progesterone to P450 21A2 was also best described by a conformational-selection model. Hexyl isonicotinate binding to P450 2E1 could be described by either a conformational-selection or an induced-fit model. Simulation of the binding of the ligands midazolam, bromocriptine, testosterone, and ketoconazole to P450 3A4 was consistent with an induced-fit or a conformational-selection model, but the concentration dependence of binding rates for varying both P450 3A4 and midazolam concentrations revealed discordance in the parameters, indicative of conformational-selection. Binding of the P450s 2C8, 2D6, 3A4, 4A11, and 21A2 was best described by conformational-selection, and P450 2E1 appeared to fit either mode. These findings highlight the complexity of human P450-substrate interactions and that conformational-selection is a dominant feature of many of these interactions.
© 2019 Guengerich et al.
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17 MeSH Terms
In vitro safety pharmacology evaluation of 2-hydroxybenzylamine acetate.
Fuller JC, Pitchford LM, Morrison RD, Daniels JS, Flynn CR, Abumrad NN, Oates JA, Boutaud O, Rathmacher JA
(2018) Food Chem Toxicol 121: 541-548
MeSH Terms: Adult, Benzylamines, Blood Proteins, Cytochrome P-450 Enzyme System, ERG1 Potassium Channel, Erythrocytes, Female, Gene Expression Regulation, Enzymologic, Hepatocytes, Humans, Male, Middle Aged, Mutagenicity Tests, Salmonella typhimurium
Show Abstract · Added April 15, 2019
2-hydroxybenzylamine (2-HOBA), a compound found in buckwheat, is a potent scavenger of reactive γ-ketoaldehydes, which are increased in diseases associated with inflammation and oxidative stress. While the potential of 2-HOBA is promising, studies were needed to characterize the safety of the compound before clinical trials. In a series of experiments, the risks of 2-HOBA-mediated mutagenicity and cardio-toxicity were assessed in vitro. The effects of 2-HOBA on the mRNA expression of select cytochrome P450 (CYP) enzymes were also assessed in cryopreserved human hepatocytes. Further, the distribution and metabolism of 2-HOBA in blood were determined. Our results indicate that 2-HOBA is not cytotoxic or mutagenic in vitro and does not induce the expression of CYP1A2, CYP2B6, or CYP3A4 in human hepatocytes. The results of the hERG testing showed a low risk of cardiac QT wave prolongation. Plasma protein binding and red blood cell distribution characteristics indicate low protein binding and no preferential distribution into erythrocytes. The major metabolites identified were salicylic acid and the glycoside conjugate of 2-HOBA. Together, these findings support development of 2-HOBA as a nutritional supplement and provide important information for the design of further preclinical safety studies in animals as well as for human clinical trials with 2-HOBA.
Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.
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MeSH Terms
The Cytochrome P450 Slow Metabolizers CYP2C9*2 and CYP2C9*3 Directly Regulate Tumorigenesis via Reduced Epoxyeicosatrienoic Acid Production.
Sausville LN, Gangadhariah MH, Chiusa M, Mei S, Wei S, Zent R, Luther JM, Shuey MM, Capdevila JH, Falck JR, Guengerich FP, Williams SM, Pozzi A
(2018) Cancer Res 78: 4865-4877
MeSH Terms: Animals, Arachidonic Acid, Arachidonic Acids, Carcinogenesis, Carcinoma, Non-Small-Cell Lung, Cell Line, Tumor, Cytochrome P-450 CYP2C9, Cytochrome P-450 Enzyme System, Eicosanoids, Endothelial Cells, Humans, Mice, Polymorphism, Single Nucleotide, Xenograft Model Antitumor Assays
Show Abstract · Added October 25, 2018
Increased expression of cytochrome P450 CYP2C9, together with elevated levels of its products epoxyeicosatrienoic acids (EET), is associated with aggressiveness in cancer. Cytochrome P450 variants and encode proteins with reduced enzymatic activity, and individuals carrying these variants metabolize drugs more slowly than individuals with wild-type , potentially affecting their response to drugs and altering their risk of disease. Although genetic differences in CYP2C9-dependent oxidation of arachidonic acid (AA) have been reported, the roles of CYP2C9*2 and CYP2C9*3 in EET biosynthesis and their relevance to disease are unknown. Here, we report that CYP2C9*2 and CYP2C9*3 metabolize AA less efficiently than CYP2C9*1 and that they play a role in the progression of non-small cell lung cancer (NSCLC) via impaired EET biosynthesis. When injected into mice, NSCLC cells expressing CYP2C9*2 and CYP2C9*3 produced lower levels of EETs and developed fewer, smaller, and less vascularized tumors than cells expressing CYP2C9*1. Moreover, endothelial cells expressing these two variants proliferated and migrated less than cells expressing CYP2C*1. Purified CYP2C9*2 and CYP2C9*3 exhibited attenuated catalytic efficiency in producing EETs, primarily due to impaired reduction of these two variants by NADPH-P450 reductase. Loss-of-function SNPs within and were associated with improved survival in female cases of NSCLC. Thus, decreased EET biosynthesis represents a novel mechanism whereby CYPC29*2 and CYP2C9*3 exert a direct protective role in NSCLC development. These findings report single nucleotide polymorphisms in the human CYP2C9 genes, and , exert a direct protective role in tumorigenesis by impairing EET biosynthesis. .
©2018 American Association for Cancer Research.
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14 MeSH Terms
Sulfenylation of Human Liver and Kidney Microsomal Cytochromes P450 and Other Drug-Metabolizing Enzymes as a Response to Redox Alteration.
Albertolle ME, Phan TTN, Pozzi A, Guengerich FP
(2018) Mol Cell Proteomics 17: 889-900
MeSH Terms: Animals, Biocatalysis, Cysteine, Cytochrome P-450 Enzyme System, Humans, Hydrogen Peroxide, Kidney, Mice, Transgenic, Microsomes, Liver, Oxidation-Reduction, Pharmaceutical Preparations, Recombinant Proteins, Staining and Labeling, Sulfenic Acids, Sulfhydryl Compounds
Show Abstract · Added March 14, 2018
The lumen of the endoplasmic reticulum (ER) provides an oxidizing environment to aid in the formation of disulfide bonds, which is tightly regulated by both antioxidant proteins and small molecules. On the cytoplasmic side of the ER, cytochrome P450 (P450) proteins have been identified as a superfamily of enzymes that are important in the formation of endogenous chemicals as well as in the detoxication of xenobiotics. Our previous report described oxidative inhibition of P450 Family 4 enzymes via oxidation of the heme-thiolate cysteine to a sulfenic acid (-SOH) (Albertolle, M. E. (2017) 292, 11230-11242). Further proteomic analyses of murine kidney and liver microsomes led to the finding that a number of other drug-metabolizing enzymes located in the ER are also redox-regulated in this manner. We expanded our analysis of sulfenylated enzymes to human liver and kidney microsomes. Evaluation of the sulfenylation, catalytic activity, and spectral properties of P450s 1A2, 2C8, 2D6, and 3A4 led to the identification of two classes of redox sensitivity in P450 enzymes: heme-thiolate-sensitive and thiol-insensitive. These findings provide evidence for a mammalian P450 regulatory mechanism, which may also be relevant to other drug-metabolizing enzymes. (Data are available via ProteomeXchange with identifier PXD007913.).
© 2018 by The American Society for Biochemistry and Molecular Biology, Inc.
1 Communities
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15 MeSH Terms
Cytochrome P450 2A6 and other human P450 enzymes in the oxidation of flavone and flavanone.
Kakimoto K, Murayama N, Takenaka S, Nagayoshi H, Lim YR, Kim V, Kim D, Yamazaki H, Komori M, Guengerich FP, Shimada T
(2019) Xenobiotica 49: 131-142
MeSH Terms: Chromatography, Liquid, Cytochrome P-450 CYP2A6, Cytochrome P-450 Enzyme System, Flavanones, Flavones, Humans, Kinetics, Mass Spectrometry, Molecular Docking Simulation, Oxidation-Reduction
Show Abstract · Added March 14, 2018
1. We previously reported that flavone and flavanone interact spectrally with cytochrome P450 (P450 or CYP) 2A6 and 2A13 and other human P450s and inhibit catalytic activities of these P450 enzymes. In this study, we studied abilities of CYP1A1, 1A2, 1B1, 2A6, 2A13, 2C9 and 3A4 to oxidize flavone and flavanone. 2. Human P450s oxidized flavone to 6- and 5-hydroxylated flavones, seven uncharacterized mono-hydroxylated flavones, and five di-hydroxylated flavones. CYP2A6 was most active in forming 6-hydroxy- and 5-hydroxyflavones and several mono- and di-hydroxylated products. 3. CYP2A6 was also very active in catalyzing flavanone to form 2'- and 6-hydroxyflavanones, the major products, at turnover rates of 4.8 min and 1.3 min, respectively. Other flavanone metabolites were 4'-, 3'- and 7-hydroxyflavanone, three uncharacterized mono-hydroxylated flavanones and five mono-hydroxylated flavones, including 6-hydroxyflavone. CYP2A6 catalyzed flavanone to produce flavone at a turnover rate of 0.72 min that was ∼3-fold higher than that catalyzed by CYP2A13 (0.29 min). 4. These results indicate that CYP2A6 and other human P450s have important roles in metabolizing flavone and flavanone, two unsubstituted flavonoids, present in dietary foods. Chemical mechanisms of P450-catalyzed desaturation of flavanone to form flavone are discussed.
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10 MeSH Terms
Inherent steroid 17α,20-lyase activity in defunct cytochrome P450 17A enzymes.
Gonzalez E, Johnson KM, Pallan PS, Phan TTN, Zhang W, Lei L, Wawrzak Z, Yoshimoto FK, Egli M, Guengerich FP
(2018) J Biol Chem 293: 541-556
MeSH Terms: Animals, Cytochrome P-450 Enzyme System, Humans, Hydroxysteroids, Protein Conformation, Steroid 17-alpha-Hydroxylase, Zebrafish
Show Abstract · Added March 14, 2018
Cytochrome P450 (P450) 17A1 catalyzes the oxidations of progesterone and pregnenolone and is the major source of androgens. The enzyme catalyzes both 17α-hydroxylation and a subsequent 17α,20-lyase reaction, and several mechanisms have been proposed for the latter step. Zebrafish P450 17A2 catalyzes only the 17α-hydroxylations. We previously reported high similarity of the crystal structures of zebrafish P450 17A1 and 17A2 and human P450 17A1. Five residues near the heme, which differed, were changed. We also crystallized this five-residue zebrafish P450 17A1 mutant, and the active site still resembled the structure in the other proteins, with some important differences. These P450 17A1 and 17A2 mutants had catalytic profiles more similar to each other than did the wildtype proteins. Docking with these structures can explain several minor products, which require multiple enzyme conformations. The 17α-hydroperoxy (OOH) derivatives of the steroids were used as oxygen surrogates. Human P450 17A1 and zebrafish P450s 17A1 and P450 17A2 readily converted these to the lyase products in the absence of other proteins or cofactors (with catalytically competent kinetics) plus hydroxylated 17α-hydroxysteroids. The 17α-OOH results indicate that a "Compound I" (FeO) intermediate is capable of formation and can be used to rationalize the products. We conclude that zebrafish P450 17A2 is capable of lyase activity with the 17α-OOH steroids because it can achieve an appropriate conformation for lyase catalysis in this system that is precluded in the conventional reaction.
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7 MeSH Terms
Kinetic Deuterium Isotope Effects in Cytochrome P450 Reactions.
Guengerich FP
(2017) Methods Enzymol 596: 217-238
MeSH Terms: Biocatalysis, Cytochrome P-450 Enzyme System, Deuterium, Enzyme Assays, Humans, Hydrogen Bonding, Kinetics, Models, Chemical, Oxidation-Reduction, Substrate Specificity
Show Abstract · Added March 14, 2018
Cytochrome P450 (P450, CYP) research provides many opportunities for the application of kinetic isotope effect (KIE) strategies. P450s collectively catalyze oxidations of more substrates than any other group of enzymes, and CH bond cleavage is a major feature in a large fraction of these reactions. The presence of a significant primary deuterium KIE is evidence that hydrogen abstraction is at least partially rate-limiting in the reactions, and this appears to be the case in many P450 reactions. The first report of a KIE in (P450-linked) drug metabolism appeared in 1961 (for morphine N-demethylation), and in a number of cases, it has been possible to modulate the in vivo metabolism or toxicity of chemicals by deuterium substitution. A number of efforts are in progress to utilize deuterium substitution to alter the metabolism of drugs in an advantageous manner.
© 2017 Elsevier Inc. All rights reserved.
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10 MeSH Terms
Nonsteroidal Anti-inflammatory Drug Interaction with Prostacyclin Synthase Protects from Miscarriage.
Velez Edwards DR, Edwards TL, Bray MJ, Torstenson E, Jones S, Shrubsole MJ, Muff HJ, Hartmann KE
(2017) Sci Rep 7: 9874
MeSH Terms: Abortion, Spontaneous, Adult, Alleles, Anti-Inflammatory Agents, Non-Steroidal, Cytochrome P-450 Enzyme System, Disease Susceptibility, Female, Genotype, Humans, Intramolecular Oxidoreductases, Odds Ratio, Polymorphism, Single Nucleotide, Pregnancy, Risk Factors
Show Abstract · Added February 21, 2019
This study evaluates the relationship between single nucleotide polymorphisms (SNPs) in nonsteroidal anti-inflammatory drug (NSAID) metabolism and related pathways and spontaneous abortion (SAB, gestation < 20 weeks) risk. Women were enrolled in Right from the Start (2004-2010) prospective cohort. Periconceptional NSAIDs reported through the sixth week of pregnancy were obtained from study interviews. We evaluated 201 SNPs in 600 European American women. Interaction analyses between NSAID use and SNPs were conducted using logistic regression, adjusted for confounders. We also evaluated prostaglandin E2 urinary metabolite (PGE-M) in an independent population for association with SNPs using linear regression. NSAID use was reported by 63% of cases and 62% controls. The most significant interaction was at prostacyclin synthase (PGIS) rs5602 (OR = 0.34, 95% CI 0.19-0.60, p = 2.45 × 10) and was significant after a Bonferroni correction. NSAID users were protected from SAB (OR = 0.78, 95% CI 0.56-1.10), while non-NSAID users were at increased risk (OR = 2.11, 95% CI 1.35-3.29) in rs5602 stratified analyses. rs5602 also associated with increased PGE-M levels (Beta = 0.09, 95% CI -0.002-0.19, p = 0.033). We identified an association between a PGIS variant and SAB risk that is modified by NSAIDs use during pregnancy and directly associated with increased levels of PGE metabolites. This suggests the potential use of genetic information to guide pharmaceutical intervention to prevent adverse pregnancy outcomes.
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14 MeSH Terms
Cytochrome P450 epoxygenase-derived epoxyeicosatrienoic acids contribute to insulin sensitivity in mice and in humans.
Gangadhariah MH, Dieckmann BW, Lantier L, Kang L, Wasserman DH, Chiusa M, Caskey CF, Dickerson J, Luo P, Gamboa JL, Capdevila JH, Imig JD, Yu C, Pozzi A, Luther JM
(2017) Diabetologia 60: 1066-1075
MeSH Terms: Animals, Cytochrome P-450 Enzyme System, Cytochrome P450 Family 2, Eicosanoids, Insulin Resistance, Islets of Langerhans, Male, Mesenteric Arteries, Mice
Show Abstract · Added April 26, 2017
AIMS/HYPOTHESIS - Insulin resistance is frequently associated with hypertension and type 2 diabetes. The cytochrome P450 (CYP) arachidonic acid epoxygenases (CYP2C, CYP2J) and their epoxyeicosatrienoic acid (EET) products lower blood pressure and may also improve glucose homeostasis. However, the direct contribution of endogenous EET production on insulin sensitivity has not been previously investigated. In this study, we tested the hypothesis that endogenous CYP2C-derived EETs alter insulin sensitivity by analysing mice lacking CYP2C44, a major EET producing enzyme, and by testing the association of plasma EETs with insulin sensitivity in humans.
METHODS - We assessed insulin sensitivity in wild-type (WT) and Cyp2c44 mice using hyperinsulinaemic-euglycaemic clamps and isolated skeletal muscle. Insulin secretory function was assessed using hyperglycaemic clamps and isolated islets. Vascular function was tested in isolated perfused mesenteric vessels. Insulin sensitivity and secretion were assessed in humans using frequently sampled intravenous glucose tolerance tests and plasma EETs were measured by mass spectrometry.
RESULTS - Cyp2c44 mice showed decreased glucose tolerance (639 ± 39.5 vs 808 ± 37.7 mmol/l × min for glucose tolerance tests, p = 0.004) and insulin sensitivity compared with WT controls (hyperinsulinaemic clamp glucose infusion rate average during terminal 30 min 0.22 ± 0.02 vs 0.33 ± 0.01 mmol kg min in WT and Cyp2c44 mice respectively, p = 0.003). Although glucose uptake was diminished in Cyp2c44 mice in vivo (gastrocnemius R 16.4 ± 2.0 vs 6.2 ± 1.7 μmol 100 g min, p < 0.01) insulin-stimulated glucose uptake was unchanged ex vivo in isolated skeletal muscle. Capillary density was similar but vascular K-induced relaxation was impaired in isolated Cyp2c44 vessels (maximal response 39.3 ± 6.5% of control, p < 0.001), suggesting that impaired vascular reactivity produces impaired insulin sensitivity in vivo. Similarly, plasma EETs positively correlated with insulin sensitivity in human participants.
CONCLUSIONS/INTERPRETATION - CYP2C-derived EETs contribute to insulin sensitivity in mice and in humans. Interventions to increase circulating EETs in humans could provide a novel approach to improve insulin sensitivity and treat hypertension.
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9 MeSH Terms
Metabolic profiles of pomalidomide in human plasma simulated with pharmacokinetic data in control and humanized-liver mice.
Shimizu M, Suemizu H, Mitsui M, Shibata N, Guengerich FP, Yamazaki H
(2017) Xenobiotica 47: 844-848
MeSH Terms: Angiogenesis Inhibitors, Animals, Cytochrome P-450 Enzyme System, Glucuronides, Hepatocytes, Humans, Liver, Metabolome, Mice, Microsomes, Liver, Thalidomide
Show Abstract · Added March 14, 2018
1. Pomalidomide has been shown to be potentially teratogenic in thalidomide-sensitive animal species such as rabbits. Screening for thalidomide analogs devoid of teratogenicity/toxicity - attributable to metabolites formed by cytochrome P450 enzymes - but having immunomodulatory properties is a strategic pathway towards development of new anticancer drugs. 2. In this study, plasma concentrations of pomalidomide, its primary 5-hydroxylated metabolite, and its glucuronide conjugate(s) were investigated in control and humanized-liver mice. Following oral administration of pomalidomide (100 mg/kg), plasma concentrations of 7-hydroxypomalidomide and 5-hydroxypomalidomide glucuronide were slightly higher in humanized-liver mice than in control mice. 3. Simulations of human plasma concentrations of pomalidomide were achieved with simplified physiologically-based pharmacokinetic models in both groups of mice in accordance with reported pomalidomide concentrations after low dose administration in humans. 4. The results indicate that pharmacokinetic profiles of pomalidomide were roughly similar between control mice and humanized-liver mice and that control and humanized-liver mice mediated pomalidomide 5-hydroxylation in vivo. Introducing one aromatic amino group into thalidomide resulted in less species differences in in vivo pharmacokinetics in control and humanized-liver mice.
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11 MeSH Terms