cytochrome P450

(redirected from Cytochrome p-450 enzyme system)

CYP11A1

A gene on chromosome 15q23-q24 that encodes a member of the cytochrome P450 superfamily of enzymes, which catalyse reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. CYP11A1 localises to the mitochondrial inner membrane and catalyses the conversion of cholesterol to pregnenolone, the first and rate-limiting step in the synthesis of the steroid hormones.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

cytochrome P450

Abbreviation: CYP
A group of enzymes present in every type of cell in the body except red blood cells and skeletal muscle cells. They are important in metabolizing substances normally present in the body such as steroids, fat-soluble vitamins, fatty acids, prostaglandins, and alkaloids. The P450 enzymes also detoxify drugs and a great number of environmental pollutants, such as carcinogens present in tobacco smoke and charcoal-broiled meat, polychlorinated biphenyls, and dioxin. Specialized types of cytochrome P450 are involved in the synthesis of nitric oxide.
See also: cytochrome
Medical Dictionary, © 2009 Farlex and Partners

cytochrome P450

A family of enzymes responsible for the detoxification and elimination of foreign substances including many drugs by hydroxylation and increasing their solubility. The group has been intensively studied because mutations of the cytochrome P450 gene have been found to be associated with a number of diseases including Addison's disease, liver cancer and Parkinson's disease. Cytochrome P450 can also interfere with drug treatment. Selective inhibitors of aromatase-specific cytochrome P450 have been developed to assist in the treatment of breast cancer.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Thus, selection of opioids that are not metabolized by the cytochrome P-450 enzyme system, such as morphine, tapentadol, or oxymorphone, might be more prudent than would selection of opioids such as codeine, fentanyl, or oxycodone, which are metabolized by the P-450 enzyme system and, therefore, may interact with other medications.
John's wort, which may have some efficacy for depression, interacts with the cytochrome P-450 enzyme system and can thereby decrease indinavir trough blood levels by 81% and nevirapine levels by 21%.
Gemfibrozil inhibits the cytochrome P-450 enzyme system. Repaglinide stimulates the release of insulin from the pancreas and is approved for treating type 2 diabetes.
Some antiepileptic drugs--carbamazepine, oxcarbazepine, phenytoin, barbiturates (phenobarbital, mephobarbital and primidone), and topiramate--enhance the cytochrome P-450 enzyme system. "This decline potentially decreases the effectiveness of hormonal methods of contraception," said Dr.

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