Genetic variants in dog cytochrome P450 2B6 and their relevance to interindividual variability of oxidations of probe drug propofol.

The cytochromes P450 (P450s) are essential drug-metabolizing enzymes. In humans, P450 genetic variants partly account for interindividual variability in drug metabolism. However, in dogs, a species often used in drug metabolism studies, the genetic variants of P450s remain to be fully investigated. In this study, the sequencing of 6344 dog genomes identified 8 variants in CYP2B6 (formerly CYP2B11), including 7 nonsynonymous variants (R74C, A83T, V103I, R145Q, Q151H, Q233L, and F389Y). Of these variants, V103I is located in a substrate recognition site, a domain crucial for enzyme function. Notably, the R74C variant exhibited a highly breed-specific distribution across the 119 dog breeds analyzed. The eighth variant, c.823-2_823delAGG, was located at the boundary of intron 5 and exon 6 and, in transcripts generated by minigene assay in human embryonic kidney 293 cells, led to the deletion of 3 bases of exon 6. This resulted in the deletion of 1 amino acid residue (p.E275del). To perform metabolic assays, recombinant proteins of all 8 variants were prepared in Escherichia coli. The metabolic activities of some variants were different from that of the reference CYP2B6 protein. These results suggest the possible contribution of genetic variants to the variability of CYP2B-dependent drug metabolism in dog liver. SIGNIFICANCE STATEMENT: Seven nonsynonymous dog cytochrome P450 2B6 variants were identified. Eighth variant, c.823-2_823delAGG, shifted the splice acceptor site, resulting in a 3-nucleotide deletion. Potential importance of CYP2B6 variants in the variability exists in metabolic activities among individual animals.