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Equine cytochrome P450 2B6--genomic identification, expression and functional characterization with ketamine
L M Peters1, S Demmel, G Pusch
1Division Veterinary Pharmacology and Toxicology, Vetsuisse Faculty, University Bern, Laenggassstr. 124, 3012 Bern, Switzerland.
Toxicology and Applied Pharmacology
|November 13, 2012
Summary
Researchers characterized equine CYP2B6, an enzyme crucial for drug metabolism in horses. This study clarifies ketamine and norketamine metabolism, identifying clopidogrel as a potential inhibitor for equine CYP2B6.
Area of Science:
- Veterinary Pharmacology
- Drug Metabolism
- Cytochrome P450 Enzymes
Background:
- Ketamine is a common anesthetic in horses, but its metabolism and drug interactions are poorly understood due to limited knowledge of equine cytochrome P450 enzymes (CYPs).
- Understanding equine CYPs is vital for predicting drug efficacy and adverse effects in horses.
Purpose of the Study:
- To characterize the equine CYP2B6 enzyme, including its annotation, cloning, and heterologous expression.
- To investigate the metabolic activity of equine CYP2B6 using ketamine and norketamine as substrates.
- To assess the inhibitory potential of clopidogrel on equine CYP2B6 activity.
Main Methods:
- Computational annotation of equine CYP2B genes.
- Cloning and heterologous expression of equine CYP2B6 in V79 Chinese hamster fibroblasts.
- Incubation of transfected cells with ketamine and norketamine to determine metabolic pathways and kinetics.
- Inhibition studies using clopidogrel to assess its effect on equine CYP2B6 activity.
Main Results:
- Equine CYP2B6 shares 77% amino acid identity with its human ortholog, with a common genetic variant (c.226G>A) found in 82% of horses studied.
- Recombinant equine CYP2B6 demonstrated N-demethylation of ketamine to norketamine and further metabolism of norketamine.
- Clopidogrel effectively inhibited equine CYP2B6-mediated N-demethylation of ketamine and norketamine, with IC50 values around 6 μM.
Conclusions:
- Equine CYP2B6 is confirmed to be involved in ketamine and norketamine metabolism.
- Clopidogrel shows potential as a specific inhibitor for equine CYP2B6, although further studies are needed to confirm specificity.
- Heterologous expression of equine CYP enzymes provides a valuable tool for understanding equine drug metabolism and interactions.
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