Drug Metabolism & Transporters

Cytochrome P450 CYP

TRSitokrom P450
Also known as:CYP450 · P450 enzymes

A superfamily of heme-containing monooxygenase enzymes, located mainly in the endoplasmic reticulum of hepatocytes and enterocytes, that catalyze most phase I oxidative drug metabolism.

In depth

CYP enzymes use electrons from NADPH–cytochrome P450 reductase and molecular oxygen to insert one oxygen atom into the substrate. Isoforms are named by family, subfamily and individual enzyme (e.g. CYP3A4); the name derives from the 450 nm absorbance peak of the reduced enzyme bound to carbon monoxide.

A few isoforms (CYP3A4/5, CYP2D6, CYP2C9, CYP2C19, CYP1A2 and CYP2B6) account for most CYP-mediated metabolism of clinically used drugs, CYP3A4 being the most important. Their activity is altered by induction, inhibition, genetic polymorphism (notably CYP2D6, CYP2C19 and CYP2C9), age and liver disease, making CYPs a major source of interindividual variability and drug interactions.

Clinical pearl

Before a strong CYP inhibitor or inducer is started or stopped, the medication list should be checked for narrow-therapeutic-index substrates of the same isoform, e.g. warfarin (CYP2C9), tacrolimus (CYP3A4) or theophylline (CYP1A2).

Example drugs

Midazolam Warfarin Theophylline Omeprazole Metoprolol
TRIn Turkish

Sitokrom P450

Başlıca hepatositlerin ve enterositlerin endoplazmik retikulumunda bulunan ve faz I oksidatif ilaç metabolizmasının büyük bölümünü katalizleyen, hem içeren monooksijenaz enzimlerinden oluşan bir süper ailedir.

CYP enzimleri NADPH–sitokrom P450 redüktazdan gelen elektronları ve moleküler oksijeni kullanarak substrata bir oksijen atomu ekler. İzoformlar aile, alt aile ve tek tek enzim düzeyinde adlandırılır (ör. CYP3A4); ad, karbon monoksite bağlı indirgenmiş enzimin 450 nm'deki absorbans pikinden gelir.

Az sayıda izoform (CYP3A4/5, CYP2D6, CYP2C9, CYP2C19, CYP1A2 ve CYP2B6) klinikte kullanılan ilaçların CYP aracılı metabolizmasının büyük bölümünden sorumludur; bunlar arasında en önemlisi CYP3A4'tür. Aktiviteleri indüksiyon, inhibisyon, genetik polimorfizm (özellikle CYP2D6, CYP2C19 ve CYP2C9), yaş ve karaciğer hastalığıyla değişir; bu nedenle CYP enzimleri bireyler arası değişkenliğin ve ilaç etkileşimlerinin başlıca kaynağıdır.

Güçlü bir CYP inhibitörü veya indükleyicisi başlanmadan ya da kesilmeden önce ilaç listesi aynı izoformun dar terapötik indeksli substratları açısından gözden geçirilmelidir; ör. varfarin (CYP2C9), takrolimus (CYP3A4) veya teofilin (CYP1A2).

Diğer adları:CYP450 · P450 enzimleri
Updated 24.09.2026 0 views Educational reference — verify against current sources before clinical use.

Read next

CYP3A4CYP3A4

The most abundant cytochrome P450 isoform in the human liver and small-intestinal epithelium, responsible for the oxidative metabolism of a large proportion of clinically used drugs.

 CYP2D6CYP2D6

A highly polymorphic cytochrome P450 enzyme that metabolises a large number of drugs, including several opioids and antidepressants, and activates key prodrugs.

 CYP2C19CYP2C19

A cytochrome P450 enzyme that activates the prodrug clopidogrel to its antiplatelet metabolite and also metabolises proton pump inhibitors and several other drugs.

 Enzyme InductionEnzim İndüksiyonu

An increase in the amount and activity of a drug-metabolizing enzyme or transporter, usually through enhanced gene transcription, caused by repeated exposure to a drug or other xenobiotic.

 Enzyme InhibitionEnzim İnhibisyonu

A reduction in the activity of a drug-metabolizing enzyme by a co-administered drug or other substance, which lowers the clearance of drugs dependent on that enzyme and raises their concentrations.

 Phase I MetabolismFaz I Metabolizma

Functionalization reactions, mainly oxidation, reduction and hydrolysis, that introduce or unmask a polar group such as –OH, –NH2 or –COOH on a drug molecule.