Equine cytochrome P450 2C92: cDNA cloning, expression and initial characterization.

This research article is about a study on the metabolic clearance of therapeutic agents in horses, particularly focusing on a cytochrome P450 monooxygenase in the 2C family. The researchers cloned, sequenced, and expressed the enzyme, showing substantial differences in metabolism of substrates between horses and humans.

Research Background

• The research was motivated by the significant gaps in understanding how therapeutic agents are metabolically cleared in horses.
• The study focused on a cytochrome P450 monooxygenase in the 2C family, which plays a crucial role in drug metabolism in mammals.

Methodology

• The researchers cloned the cytochrome P450 monooxygenase from an equine liver and sequenced it.
• Upon sequencing, the protein was expressed in a baculovirus expression system, which is a commonly used method to produce recombinant proteins.
• Next, they measured the catalytic activities of the recombinant protein with various substrates.
• The specific protein in the study was assigned CYP2C92.

Key Findings

• The CYP2C92 protein exhibited optimal catalytic activity with the drug diclofenac using molar ratios of CYP2C92 to NADPH CYP450 reductase of 1:18.
• Addition of cytochrome b(5) to diclofenac incubations had no significant impact on metabolic turnover, which is the rate at which drugs are metabolized.
• Notably, CYP2C92 catalyzed diclofenac metabolism was discovered to be 20 times slower than its human equivalent, CYP2C9.
• However, CYP2C92 demonstrated similar levels of tolbutamide and (S)-warfarin hydroxylase activity to CYP2C9 when b(5) was added to reactions.

Conclusion

• The study highlighted significant differences in the metabolism of substrates by CYP2C orthologues between horses and humans.
• This underscores the need for comprehensive characterization of this enzyme system in horses (equids) to advance veterinary pharmacology and ensure more effective and safe drug administration in these animals.