Cytochrome P450's (CYPs) are heme-containing enzymes involved in the metabolism of
drugs, hormones, and environmental chemicals. These membrane-bound enzymes are expressed
in the endoplasmic reticulum of the liver, intestine, kidney, brain, adrenal, and
other organs. There are hundreds of CYPs recognized; CYP enzymes are categorized within
and between different species using a family/subfamily/individual enzyme nomenclature
[
[1]
]. For example, CYP3A4, an abundant P450 in human liver, is a member of the CYP3 family
and CYP3A subfamily and represents a unique enzyme (3A4) in human beings. The ortholog
(comparable enzyme) in dogs is CYP3A12. Orthologs among species are evolutionarily
related, share high amino acid identity, and may share similar substrate ranges. There
can also be unexpected differences in substrate specificity among orthologous P450
enzymes between species, however. This has important implications for attempts to
extrapolate known drug interactions from people to veterinary patients.To read this article in full you will need to make a payment
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