Pharmacology Book


Cytochrome P-450

Aka: Cytochrome P-450, Cytochrome P450, CYP450, Cytochrome P450 Induction
  1. See Also
    1. P-Glycoprotein
  2. Background
    1. Cytochrome P450 is central to hepatic metabolism of medications
      1. Cytochrome P450 is named for its maximal light absorption wave length of 450 nm
      2. Hepatocytes in the liver contain a P450 family of microsomal enzymes on the endoplasmic reticulum
    2. Cytochrome P450 enzymes are responsible for 80% of drug-Drug Interactions
    3. Primary role of CYP enzymes is to facilitate drug excretion by increasing drug polarity and hence water solubility
      1. P450 Enzymes facilitate drug oxidation and reduction, utilizing NADPH donated electrons (Phase 1 Reaction)
    4. Cytochrome P450 enzymes may be induced to greater activity
      1. Certain drugs stimulate an increased production and activity of specific CYP450 isoenzymes
      2. Increased isoenzyme levels increase metabolism of both inducer drugs, AND other drugs metabolized by the same isoenzyme
      3. Examples: Alcohol, Carbamazepine, Phenytoin, St. John's Wort
  3. Types: Cytochrome P-450 Isoenzymes
    1. Hepatic Isoenzymes
      1. CYP3As (40-60% hepatic P-450 isoenzymes)
      2. CYP2D6 (2-5% hepatic P-450 isoenzymes)
      3. CYP2As (<1% hepatic P-450 isoenzymes)
      4. CYP1A2
      5. CYP2Cs
    2. Other Isoenzymes
      1. CYP1A1
      2. CYP2Bs
      3. CYP2E1
      4. CYP4As
  4. References
    1. (1999) Med Lett Drugs Ther 41(1056): 61-2 [PubMed]
    2. Ament (2000) Am Fam Physician 61(6): 1745-54 [PubMed]
    3. Bhatia (1997) Am Fam Physician 55(5):1683-94 [PubMed]
    4. Flockhart (2002) Arch Intern Med 162:405-12 [PubMed]
    5. Johnson (1999) Postgrad Med 105(2):193-222 [PubMed]

Cytochrome P450 (C0010762)

Definition (NCI_NCI-GLOSS) A group of enzymes involved in drug metabolism and found in high levels in the liver. These enzymes change many drugs, including anticancer drugs, into less toxic forms that are easier for the body to excrete.
Definition (NCI) A family of cytochromes that are involved in electron transport and oxidative metabolism of drugs and other bioactive molecules. When the catalytic heme is reduced the absorbance peak for this protein occurs at 450 nm.
Definition (MSH) A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.
Definition (CSP) superfamily of closely related heme enzymes found throughout the phylogenetic spectrum; they catalyze the insertion of an atom of oxygen into substrates; in animals, these P-450 enzymes are involved in biosynthesis of steroids, fatty acids, and bile acids and also in metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs.
Concepts Amino Acid, Peptide, or Protein (T116) , Enzyme (T126)
MSH D003577
SnomedCT 424446007
English Cytochrome P 450, Cytochrome P-450, Cytochrome P450, cytochrome P450, Cytochrome p450 enzyme, Cytochrome p-450, Cytochrome p450 enzyme (substance), Cytochrome p-450 enzyme, Cytochrome p450, CYTOCHROME P 450 ENZYME SYSTEM, CYTOCHROME P 450, Cytochrome P-450 Enzyme System [Chemical/Ingredient], cytochrome p450, cytochrome p 450, cytochromes p450, p450 cytochrome, cytochrome p-450, Cytochrome P 450 Enzyme System, Cytochrome P-450 Enzyme System, cytochrome P450 enzyme system, Enzymes, Cytochrome P-450, Enzymes, P450, Cytochrome P-450 Enzymes, Cytochrome P 450 Enzymes, P-450 Enzymes, Cytochrome, P-450 Enzymes, P450 Enzymes, Enzymes, P-450, P 450 Enzymes, P450, CYP (cytochrome P450)
French Système cytochrome P450, Cytochrome P-450 enzyme system, Système enzymatique du cytochrome P-450
Swedish Cytokrom P-450
Spanish enzima de citocromo p450, citocromo p-450, citocromo p450, enzima de citocromo p450 (sustancia), Citocromo P-450, Sistema Enzimático del Citocromo P-450
Czech systém (enzymů) cytochromů P-450, cytochrom P-450, CYP-dependentní monooxygenasa
Finnish Sytokromi P-450 -entsyymijärjestelmä
Japanese シトクロームP450, シトクロムP-450依存性モノオキシゲナーゼ, シトクロムP450, チトクロームP450, チトクロムP-450, チトクロームP-450, チトクロームP-450-依存性モノオキシゲナーゼ, チトクロムP450, シトクロームP-450, シトクロムP-450
Italian Citocromo P-450, Citocromo P450, Sistema enzimatico del citocromo P-450
German CYTOCHROM P 450, CYTOCHROM P 450 ENZYM SYSTEM, ZYTOCHROM P 450, Cytochrom P-450, Zytochrom P-450, Cytochrom-P-450-Enzym-System
Polish System enzymatyczny cytochromu P-450, Układ enzymatyczny cytochromu P-450, Cytochrom P-450
Norwegian Cytokrom P-450-enzymsystemet, Cytokrom P-450
Portuguese Monoxigenase Citocromo P-450-Dependente, Monoxigenase Dependente de Citocromo P-450, Sistema de Enzimas Citocromo P-450, Mono-Oxigenase Citocromo P-450-Dependente, Citocromo P-450, Sistema Enzimático do Citocromo P-450
Derived from the NIH UMLS (Unified Medical Language System)

You are currently viewing the original '\legacy' version of this website. Internet Explorer 8.0 and older will automatically be redirected to this legacy version.

If you are using a modern web browser, you may instead navigate to the newer desktop version of fpnotebook. Another, mobile version is also available which should function on both newer and older web browsers.

Please Contact Me as you run across problems with any of these versions on the website.

Navigation Tree