Enzymes Involved in Drug Metabolism (e.g., Cytochrome P450)
Start with the big picture
Phase I metabolism commonly involves oxidation, reduction, or hydrolysis, introducing or exposing functional groups. Phase II enzymes attach hydrophilic groups to drugs or their Phase I metabolites, generally increasing water solubility and supporting excretion. Major Phase I enzymes include CYPs, flavin-containing monooxygenases, dehydrogenases, esterases, and epoxide hydrolase; Phase II families include UGT, SULT, NAT, GST, and methyltransferases. CYP enzymes are especially relevant to drug metabolism: differences in their activity can alter drug effects or toxicity, while inhibition and induction contribute to drug–drug interactions. The lesson connects these enzyme systems with examples involving CYP3A4, CYP2D6, CYP2C9, CYP2C19, CYP1A2, CYP2E1, UGT1A1, and GST.
What you'll learn
- Distinguish Phase I functionalization from Phase II conjugation.
- Identify major enzyme families involved in Phase I and Phase II metabolism.
- Describe the role of CYP enzymes in drug metabolism.
- Relate selected CYP and UGT variations or interactions to clinical effects.
- Explain how enzyme inhibition and induction can contribute to drug–drug interactions.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
