CYP1

CYP1 refers to the cytochrome P450 family 1, a group of enzymes encoded by three genes in humans: CYP1A1, CYP1A2, and CYP1B1. These enzymes are heme-thiol monooxygenases that catalyze the oxidation of a broad range of substrates, including environmental xenobiotics such as polycyclic aromatic hydrocarbons (PAHs), as well as endogenous compounds like estrogens and fatty acids. Members of the CYP1 family are primarily regulated by the aryl hydrocarbon receptor (AHR), and their expression is inducible upon exposure to AHR ligands (for example, dioxins and PAHs) via xenobiotic response elements in their promoters.

CYP1A1 is expressed mainly in extrahepatic tissues, notably the lung, and plays a key role in activation of procarcinogens such as benzo[a]pyrene to reactive metabolites capable of DNA adduct formation. CYP1A2 is predominantly hepatic and contributes to the metabolism of several clinically important compounds, including caffeine and theophylline, as well as various drugs and carcinogens. CYP1B1 is widely expressed, with high levels in reproductive tissues and certain cancers, and is notable for metabolizing estrogens to 4-hydroxy metabolites, a pathway linked to estrogen-related carcinogenesis. Mutations in CYP1B1 are a major cause of primary congenital glaucoma and can affect tissue-specific metabolism.

Clinical and research relevance includes interindividual variability in CYP1A2 and CYP1B1 activity due to genetic polymorphisms and environmental exposure, influencing drug clearance and cancer risk. Pharmacogenomic considerations arise when evaluating drug dosing and toxicology in the context of CYP1 enzyme activity.