Mechanistic study of allopurinol oxidation using aldehyde oxidase, xanthine oxidase and cytochrome P450 enzymes

RSC Advances ◽  
2016 ◽  
Vol 6 (111) ◽  
pp. 109672-109680 ◽  
Author(s):  
Saber Mirzaei ◽  
Avat Arman Taherpour ◽  
Shahryar Mohamadi
Keyword(s):  
Cytochrome P450 ◽  
Xanthine Oxidase ◽  
Active Metabolite ◽  
Oxidation Reaction ◽  
Aldehyde Oxidase ◽  
Mechanistic Study ◽  
Inhibitory Mechanism ◽  
Cytochrome P450 Enzymes ◽  
P450 Enzyme

The oxidation reaction of allopurinol to its active metabolite (oxypurinol) is investigated using the AO and P450 enzymes. To the contrary of AO (and XO), the P450 enzyme can metabolize the allopurinol with a not self-inhibitory mechanism.

scholarly journals Exploring the effect of khat (Catha edulis) chewing on the pharmacokinetics of the antiplatelet drug clopidogrel in rats using the newly developed LC-MS/MS technique

2020 ◽  
Vol 18 (1) ◽  
pp. 681-690
Author(s):  
Hassan A. Alhazmi ◽  
Adnan A. Kadi ◽  
Mohamed W. Attwa ◽  
Waquar Ahsan ◽  
Manal Mohamed Elhassan Taha ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Active Metabolite ◽  
Dose Adjustment ◽  
Internal Standard ◽  
Cardiovascular Complications ◽  
Antiplatelet Drug ◽  
Peak Ratio ◽  
Cytochrome P450 Enzymes ◽  
Time Intervals ◽  
Addictive Substance

AbstractClopidogrel (CLOP) is widely used worldwide for cardiovascular complications. CLOP is highly metabolized in the liver to its active metabolite by cytochrome P450 enzymes. Studies have shown that khat, an addictive substance, is a powerful inhibitor of cytochrome P450 enzymes and can influence the metabolism of drugs that are concomitantly used. Therefore, this study was designed to evaluate the effects of khat on the pharmacokinetics of CLOP in rats. In this study, rats were administered either CLOP alone or CLOP combined with khat and their plasma were obtained at different time intervals and analyzed using the newly developed and validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) method using foretinib (FTB) as the internal standard. The corresponding peak area of the analyte versus FTB was used for calculating the peak ratio. The validated LC-MS/MS method resulted in the separation of the well-defined quantifiable peaks of CLOP, FTB, and CLOP metabolite within 7 min. Results showed a significant influence of khat on the peak ratio of CLOP metabolite, which was found to be significantly decreased (P < 0.05) in comparison to CLOP alone, suggesting significant decrease in the conversion of CLOP to its active metabolite due to the inhibition of CYP450 enzymes by khat. Therefore, there might be a need for dose adjustment for regular khat chewers using CLOP.

Drug Interactions of Macrolides: Emphasis on Dirithromycin

1997 ◽  
Vol 31 (3) ◽  
pp. 349-356 ◽  
Author(s):  
Vish S Watkins ◽  
Ron E Polk ◽  
Jennifer L Stotka
Keyword(s):  
Cytochrome P450 ◽  
Drug Interactions ◽  
Ethinyl Estradiol ◽  
Enzyme System ◽  
Cytochrome P450 Enzyme ◽  
Cytochrome P450 Enzymes ◽  
Kidney Transplant Recipients ◽  
P450 Enzyme ◽  
Cytochrome P450 Enzyme System ◽  
Clinically Significant

Objective To describe the drug interactions of dirithromycin, a new macrolide, and to compare them with those of other macrolides. Data Sources A literature search was performed using MEDLINE to identify articles published between January 1980 and July 1995 concerning the drug interactions of macrolides. Published abstracts were also examined. All studies using dirithromycin were performed under the sponsorship of Eli Lilly and Company. Data Synthesis Erythromycin, the first macrolide discovered, is metabolized by the cytochrome P450 enzyme system. By decreasing their metabolism, erythromycin can interact with other drugs metabolized by the cytochrome P450 enzymes. The lack of such interactions would be a desirable feature in a newer macrolide. We describe studies performed to detect any interactions of dirithromycin with cyclosporine, theophylline, terfenadine, warfarin, and ethinyl estradiol. The studies showed that dirithromycin, like azithromycin, is much less likely to cause the interactions detected with clarithromycin and erythromycin. A review of the literature showed differences among macrolides in their abilities to inhibit cytochrome P450 enzymes and, thus, to cause drug–drug interactions. Erythromycin and clarithromycin inhibit cytochrome P450 enzymes, and have been implicated in clinically significant interactions. Azithromycin and dirithromycin neither inhibit cytochrome P450 enzymes nor are implicated in clinically significant drug–drug interactions. Conclusions Dirithromycin, a new macrolide, does not inhibit the cytochrome P450 enzyme system. The concomitant use of dirithromycin with cyclosporine, theophylline, terfenadine, warfarin, or ethinyl estradiol was studied in pharmacokinetic and pharmacodynamic studies. In vitro, dirithromycin did not bind cytochrome P450. In healthy subjects, erythromycin increases the clearance of cyclosporine by 51%, whereas dirithromycin causes no significant changes in the pharmacokinetics of cyclosporine. In kidney transplant recipients, administration of dirithromycin was associated with a significant (p < 0.003) decrease of 17.4% in the clearance of cyclosporine. In patients taking low-dose estradiol, the administration of dirithromycin caused a significant (p < 0.03) increase of 9.9% in the clearance of ethinyl estradiol; escape ovulation did not occur. Unlike erythromycin and clarithromycin, dirithromycin had no significant effects on the pharmacokinetics of theophylline, terfenadine, or warfarin. The alterations typical of drug interactions that are based on inhibition of the cytochrome P450 system occurring with erythromycin and clarithromycin were not observed with dirithromycin.

scholarly journals Characterization of Medicago truncatula (barrel medic) hydroperoxide lyase (CYP74C3), a water-soluble detergent-free cytochrome P450 monomer whose biological activity is defined by monomer–micelle association

2006 ◽  
Vol 395 (3) ◽  
pp. 641-652 ◽  
Author(s):  
Richard K. Hughes ◽  
Eric J. Belfield ◽  
Mylrajan Muthusamay ◽  
Anuja Khan ◽  
Arthur Rowe ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Cytochrome P450 ◽  
Medicago Truncatula ◽  
Water Soluble ◽  
Hydroperoxide Lyase ◽  
Cytochrome P450 Enzyme ◽  
Cytochrome P450 Enzymes ◽  
P450 Enzyme ◽  
Detergent Micelles

We describe the detailed biochemical characterization of CYP74C3 (cytochrome P450 subfamily 74C3), a recombinant plant cytochrome P450 enzyme with HPL (hydroperoxide lyase) activity from Medicago truncatula (barrel medic). Steady-state kinetic parameters, substrate and product specificities, RZ (Reinheitszahl or purity index), molar absorption coefficient, haem content, and new ligands for an HPL are reported. We show on the basis of gel filtration, sedimentation velocity (sedimentation coefficient distribution) and sedimentation equilibrium (molecular mass) analyses that CYP74C3 has low enzyme activity as a detergent-free, water-soluble, monomer. The enzyme activity can be completely restored by re-activation with detergent micelles, but not detergent monomers. Corresponding changes in the spin state equilibrium, and probably co-ordination of the haem iron, are novel for cytochrome P450 enzymes and suggest that detergent micelles have a subtle effect on protein conformation, rather than substrate presentation, which is sufficient to improve substrate binding and catalytic-centre activity by an order of magnitude. The kcat/Km of up to 1.6×108 M−1·s−1 is among the highest recorded, which is remarkable for an enzyme whose reaction mechanism involves the scission of a C–C bond. We carried out both kinetic and biophysical studies to demonstrate that this effect is a result of the formation of a complex between a protein monomer and a single detergent micelle. Association with a detergent micelle rather than oligomeric state represents a new mechanism of activation for membrane-associated cytochrome P450 enzymes. Highly concentrated and monodispersed samples of detergent-free CYP74C3 protein may be well suited for the purposes of crystallization and structural resolution of the first plant cytochrome P450 enzyme.

Inhibitory Effects of Garcinia cambogia Extract on CYP2B6 Enzyme Activity

Planta Medica ◽  
2017 ◽  
Vol 83 (11) ◽  
pp. 895-900 ◽  
Author(s):  
Jun Yu ◽  
Min Choi ◽  
Jong Park ◽  
Shaheed Rehman ◽  
Katsunori Nakamura ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Enzyme Activities ◽  
Liver Microsomes ◽  
Cytochrome P450 Enzyme ◽  
Dependent Manner ◽  
Cytochrome P450 Enzymes ◽  
Inhibitory Effects ◽  
Concentration Dependent Manner ◽  
Garcinia Cambogia ◽  
P450 Enzyme

AbstractThis study assessed the inhibitory effects of Garcinia cambogia extract on the cytochrome P450 enzymes in vitro. G. cambogia extract was incubated with cytochrome P450 isozyme-specific substrates in human liver microsomes and recombinant CYP2B6 isozyme, and the formation of the marker metabolites was measured to investigate the inhibitory potential on cytochrome P450 enzyme activities. The results showed that G. cambogia extract has significant inhibitory effects on CYP2B6 activity in a concentration-dependent manner. Furthermore, the inhibition was potentiated following preincubation with NADPH, indicating that G. cambogia extract is a time-dependent inhibitor of CYP2B6. Meanwhile, hydroxycitric acid, the major bioactive ingredient of G. cambogia extract, did not exhibit significant inhibition effects on cytochrome P450 enzyme activities. G. cambogia extract could modulate the pharmacokinetics of CYP2B6 substrate drugs and lead to interactions with those drugs. Therefore, caution may be required with respect to concomitant intake of dietary supplements containing G. cambogia extract with CYP2B6 substrates.

scholarly journals The crystal structure of the cytochrome P450 enzyme TxtE

2014 ◽  
Vol 70 (a1) ◽  
pp. C1683-C1683
Author(s):  
Feng Yu ◽  
Minjun Li ◽  
Chunyan Xu ◽  
Zhijun Wang ◽  
Huan Zhou ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Cytochrome P450 ◽  
Substrate Recognition ◽  
Industrial Applications ◽  
Cytochrome P450 Enzyme ◽  
Cytochrome P450 Enzymes ◽  
Dominant Form ◽  
Thaxtomin A ◽  
Access Channel ◽  
P450 Enzyme

Thaxtomins, a family of phytotoxins produced by Streptomyces spp., can causes plant cell necrosis at nanomolar concentrations. Thaxtomin A is the dominant form from Streptomyces scabies and has demonstrated herbicidal action. TxtE, a cytochrome P450 enzyme from S. scabies 87.22, catalyzes direct nitration of the indolyl moiety of L-tryptophan to L-4-nitrotryptophan using nitric oxide, dioxygen and NADPH, which is the key step of Thaxtomin A biosynthesis. NO-related nitration is a common chemical process in organisms, particularly for tyrosine nitration. However, TxtE is the first reported enzyme that catalyzes a direct nitration reaction specifically in a biosynthetic pathway and thus it can potentially be developed for industrial applications. The crystal structure of TxtE was determined at 2.1 angstrom. A clearly defined substrate access channel is observed and can be classified as channel 2a, which is common in bacteria cytochrome P450 enzymes. A continuous hydrogen bond chain from the active site to the external solvent is observed. Compared with other cytochrome P450 enzymes, TxtE shows a unique proton transfer pathway which crosses the helix I distortion. Polar contacts of Arg59, Tyr89, Asn293, Thr296, and Glu394 with L-tryptophan are seen using molecular docking analysis, which are potentially important for substrate recognition and binding. After mutating Arg59, Asn293, Thr296 or Glu394 to leucine, the substrate binding ability of TxtE was lost or decreased significantly. According to docking and mutagenesis experiments, we propose a possible substrate recognition and binding mechanism, a possible mechanism for substrate recognition and binding is proposed.

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