The name derives from a spectrophotometric property: when the reduced (ferrous) form of the enzyme binds carbon monoxide, the resulting complex absorbs light at a wavelength of approximately 450 nanometres. Human beings express more than 50 distinct CYP isoforms, each encoded by a separate gene and designated by a family number, a subfamily letter, and an individual numeral , for example, CYP3A4, CYP2D6, and CYP1A2. These three isoforms alone account for the biotransformation of the majority of clinically used medicines.
CYP enzymes function primarily in phase I metabolic reactions, introducing or unmasking polar functional groups on lipophilic molecules to render them more water-soluble and excretable. The catalytic cycle involves the sequential binding of the substrate, reduction of the iron centre, incorporation of molecular oxygen, and ultimately insertion of one oxygen atom into the substrate whilst the other is reduced to water.
Considerable inter-individual variation in CYP activity arises from genetic polymorphisms, age, nutritional status, and concurrent exposure to other compounds. Substances that inhibit or induce specific CYP isoforms can alter the plasma concentrations of co-administered drugs , a mechanism underlying many clinically significant drug–drug and drug–plant interactions. Constituents of Cannabis sativa, for instance, are known substrates and inhibitors of several CYP isoforms, a consideration relevant to research into cannabinoid pharmacokinetics.
In drug development and regulatory science, CYP interaction profiling is a standard preclinical requirement. The Therapeutic Goods Administration (TGA) references internationally harmonised guidance , including ICH guideline M12 on drug interaction studies; when evaluating the metabolic characteristics of new chemical entities submitted for registration on the Australian Register of Therapeutic Goods (ARTG).
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