Cytochrome P450

Cytochrome P450 is a family of heme-containing enzymes that oxidize diverse chemicals, including drugs, hormones, fatty acids, and environmental contaminants.

Heme: Heme is an iron-containing cofactor that supports electron transfer and catalysis in proteins. Its iron atom binds oxygen and enables P450 oxidation reactions.
Drug metabolism: Drug metabolism is the enzymatic transformation of medicines into metabolites that can differ in activity, distribution, and elimination. P450 enzymes perform many of the oxidation steps that determine how long drugs persist.
Cytochrome: A cytochrome is a heme-containing protein that participates in electron transfer or catalysis. P450 belongs to this broader group, though its heme also activates oxygen for oxidation.
Flavin-containing monooxygenase: Flavin-containing monooxygenases are enzymes that oxidize nucleophilic compounds using flavin cofactors and NADPH. They can oxidize some drugs also handled by P450, but use different catalytic chemistry.
Pharmacogenomics: Pharmacogenomics studies how genetic variation influences responses to medicines. Variants in genes such as CYP2D6 can alter drug metabolism and dosing needs.
Monooxygenase: A monooxygenase is an enzyme that inserts one oxygen atom from molecular oxygen into a substrate. P450 enzymes belong to this enzyme class and leave the second oxygen atom in water.
CYP3A4: CYP3A4 is a human cytochrome P450 enzyme that metabolizes many medicines and other foreign compounds. It is a major contributor to the metabolism of drugs in the intestine and liver.
Heme-thiolate protein: A heme-thiolate protein coordinates heme iron with a cysteine sulfur from the protein. The distinctive sulfur ligand tunes the P450 heme for oxygen activation.
Alcohol dehydrogenase: Alcohol dehydrogenases are enzymes that reversibly oxidize alcohols using nicotinamide cofactors. They oxidize alcohols through a different cofactor-based mechanism from P450 oxygen insertion.
Drug interaction: A drug interaction occurs when one medicine changes the effects or handling of another substance. Inhibition or induction of P450 enzymes can change the concentration of coadministered drugs.

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