CYP1A

CYP1A refers to the cytochrome P450 1A subfamily of enzymes, a group within the larger cytochrome P450 superfamily that metabolizes a wide range of endogenous and exogenous compounds. The human subfamily includes two main enzymes, CYP1A1 and CYP1A2. Like other cytochrome P450 enzymes, they are heme-containing monooxygenases located in the endoplasmic reticulum and rely on NADPH-cytochrome P450 reductase for electron transfer. They participate in Phase I metabolism and contribute to both detoxification and activation of various chemicals, including environmental pollutants and some drugs.

CYP1A1 is expressed at low constitutive levels in most adult tissues but is highly inducible in extrahepatic sites such as the lung and placenta. It is best known for activating procarcinogens such as benzo[a]pyrene to reactive metabolites that can form DNA adducts, contributing to carcinogenic risk under exposure to certain pollutants. Expression is strongly driven by activation of the aryl hydrocarbon receptor (AhR), which responds to various environmental ligands, including polycyclic aromatic hydrocarbons.

CYP1A2 is predominantly expressed in the liver and is responsible for the metabolism of several clinically important substrates, including caffeine, theophylline, and certain antipsychotics. It is inducible by exposure to AhR ligands such as tobacco smoke, which can increase drug clearance in smokers. Genetic polymorphisms also contribute to interindividual variability in CYP1A2 activity, influencing both drug response and toxicity risk.

Clinical relevance of the CYP1A family includes its role in drug interactions, interindividual variability in metabolism, and the activation of environmental procarcinogens. Understanding CYP1A activity aids in predicting metabolic capacity and assessing exposure-related health risks.