Cytochrome P450 2C19 (abbreviated CYP2C19) is an enzyme protein. It is a member of the CYP2C subfamily of the cytochrome P450 mixed-function oxidase system. This subfamily includes enzymes that catalyze metabolism of xenobiotics, including some proton pump inhibitors and antiepileptic drugs. In humans, it is the CYP2C19 gene that encodes the CYP2C19 protein. [3] [4] CYP2C19 is a liver enzyme that acts on at least 10% of drugs in current clinical use, [5] most notably the antiplatelet treatment clopidogrel (Plavix), drugs that treat pain associated with ulcers, such as omeprazole, antiseizure drugs such as mephenytoin, the antimalarial proguanil, and the anxiolytic diazepam. [6]
CYP2C19 has been annotated as (R)-limonene 6-monooxygenase and (S)-limonene 6-monooxygenase in UniProt.
The gene encodes a member of the cytochrome P450 superfamily of enzymes. Enzymes in the CYP2C subfamily, including CYP2C19, account for approximately 20% of cytochrome P450 in the adult liver. [7] These proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This protein localizes to the endoplasmic reticulum and is known to metabolize many drugs. Polymorphism within this gene is associated with variable ability to metabolize drugs. The gene is located within a cluster of cytochrome P450 genes on chromosome no.10 arm q24. [8]
CYP2C19 also possesses epoxygenase activity: it is one of the principal enzymes responsible for attacking various long-chain polyunsaturated fatty acids at their double (i.e. alkene) bonds to form epoxide products that act as signaling agents. It metabolizes:
Along with CYP2C19, CYP2C8, CYP2C9, CYP2J2, and possibly CYP2S1 are the main producers of EETs and, very likely EEQs, EDPs, and the epoxides of linoleic acid. [10] [12]
Pharmacogenomics is a study that analyzes how an individual's genetic makeup affects the response to drugs of this individual. There are many common genetic variations that affect the expression of the CYP2C19 gene, which in turn influences the enzyme activity in the metabolic pathways of those drugs in which this enzyme is involved.
The Clinical Pharmacogenetics Implementation Consortium (CPIC) provides therapeutic guidelines that are widely utilized to suggest suitable treatment plans. These recommendations are particularly relevant for patients requiring antiplatelet medication and are based on the results of genotype testing. A key aspect of these CPIC guidelines is the translation of genotype to phenotype, a process that relies on the "star" nomenclature system [13] maintained by the Pharmacogene Variation Consortium [14] assigns labels to known polymorphisms that affect drug response. A label consists of a star (asterisk) character (*) followed by a number. The most common variant (also called wild type) has "CYP2C19*1" label. The variant genotypes of CYP2C19*2 (NM_000769.2:c.681GA; p.Pro227Pro; rs4244285), CYP2C19*3 (NM_000769.2:c.636G>A; p.Trp212Ter; rs4986893) and CYP2C19*17 (NM_000769.2:c.-806C>T; rs12248560) [15] are major factors attributed to interindividual differences in the pharmacokinetics and response to CYP2C19 substrates.
CYP2C19*2 and *3 (loss-of-function alleles) are associated with diminished enzyme activity, [16] [17] whereas CYP2C19*17 (gain-of-function allele) results in increased activity. [18] The Working Group of the Association for Molecular Pathology Clinical Practice Committee recommended these three variant alleles to be included in the minimal clinical pharmacogenomic testing panel, called tier 1. The extended panel of variant alleles, called tier 2, additionally includes the following CYP2C19 alleles: *4.001 (*4A), *4.002 (*4B), *5, *6, *7, *8, *9, *10, and *35, all of them associated with diminished enzyme activity. Although these tier 2 alleles are included in many platforms, they were not included in the tier 1 recommendations because of low minor allele frequency (which can increase false-positive occurrences), less well-characterized impact on CYP2C19 function, or a lack of reference materials. In partnership with the clinical testing community, the Centers for Disease Control and Prevention established the Genetic Testing Reference Material Program to meet the need for publicly available characterized reference materials. Its goal is to improve the supply of publicly available and well-characterized genomic DNA used as reference materials for proficiency testing, quality control, test development/validation, and research studies. [15]
The allele frequencies of CYP2C19*2 and *3 are significantly higher in Chinese populations than in European or African populations, [19] and are found at approximately 3–5% of European and 15–20% of Asian populations. [20] [21] Among Arab population, the frequency of CYP2C19 genotypes including *1/*17, *1/*2, *2/*2, *3/*3, and *1/*3 were 20.2%, 16.7%, 6.1%, 5.45%, 0.7%, and 0.35%, respectively. [22] In a study of 2.29 million direct-to-consumer genetics research participants, the overall frequencies of *2, *3, and *17 were 15.2%, 0.3%, and 20.4%, respectively, but varied by ethnicity. The most common variant diplotypes were *1/*17 at 26% and *1/*2 at 19.4%. The less common *2/*17, *17/*17 and *2/*2 genotypes occurred at 6.0%, 4.4%, and 2.5%, respectively. Overall, 58.3% of participants had at least one increased-function or no-function CYP2C19 allele. [23]
CYP2C19 is involved in processing or metabolizing at least 10% of commonly prescribed drugs. [24] Variations to the enzyme can have a wide range of impacts to drug metabolism. In patients with an abnormal CYP2C19 variant certain benzodiazepines should be avoided, such as diazepam (Valium), lorazepam (Ativan), oxazepam (Serax), and temazepam (Restoril). [25] Other categories of drugs impacted by modified CYP2C19 include proton pump inhibitors, anticonvulsants, hypnotics, sedatives, antimalarial drugs, and antiretroviral drugs. [24]
On the basis of their ability to metabolize (S)-mephenytoin or other CYP2C19 substrates, individuals can be classified as ultrarapid metabolizers (UM), extensive metabolizers (EM) or poor metabolizers (PM). [21] [26] In the case of proton pump inhibitors, PMs exhibit a drug exposure that is 3 to 13 times higher than that of EMs. [27] Loss-of-function alleles, CYP2C19*2 and CYP2C19*3 (and others, which are the subject of ongoing research) predict PMs, [21] and the gain-of-function CYP2C19*17 allele predicts UMs. [24]
Although the amount of CYP2C19 enzyme produced by the *17 allele is greater than of the *1 allele, [28] whether the carriers of the *17 allele experience any significant difference in response to drugs compared to the wild-type, is a topic of ongoing research, studies show varying results. [26] [29] Some studies have found that the *17 variant's effect on the metabolism of omeprazole, pantoprazole, escitalopram, sertraline, voriconazole, tamoxifen and clopidogrel [26] [30] is modest, particularly compared to the impact of loss-of-function alleles (*2, *3), therefore, in case of these medications, the EM designation is sometimes applied instead of the UM one. [26] For example, carriers of the *17 allele did not demonstrate different gastric pH comparing to *1 after taking the proton pump inhibitor omeprazole, a CYP2C19 substrate. [26] Other studies concluded that the *17 allele seems to be the factor responsible for lower response to some drugs, even at higher doses, for example, to escitalopram for symptom remission in major depressive disorder patients. [29] CYP2C19*17 carrier status is significantly associated with enhanced response to clopidogrel and an increased risk of bleeding; the highest risk was observed for CYP2C19*17 homozygous patients. [31] [32] A study found that escitalopram serum concentration was 42% lower in patients homozygous for CYP2C19*17. [33] An important limitation of all these studies is the single-gene analysis, since most drugs that are metabolized by CYP2C19 are also metabolized by CYP2D6 and CYP3A4 enzymes. Besides that, other genes are involved in drug response, for example, escitalopram is transported by P-glycoprotein, encoded by the ABCB1 gene. In order for the studies on CYP2C19*17 to be conclusive, the differences in other genes that affect drug response have to be excluded. [29] The prevalence of the CYP2C19*17 variant is less than 5% in Asian populations and is approximately four times higher in European and African populations. [26]
The alleles CYP2C19*2 [34] and *3 may reduce the efficacy of clopidogrel (Plavix), an antiplatelet medication. The basis for this reduced effect of clopidogrel in patients who have a gene of reduced activity may seem somewhat paradoxical, but can be understood as follows. Clopidogrel is administered as a "prodrug", a drug that is inactive when taken, and then depends on the action of an enzyme in the body to be activated. In patients with a gene of reduced activity, clopidogrel may not be metabolized to its biologically active form and therefore not achieve pharmacological effect in the body. The relative risk of major cardiac events among patients treated with clopidogrel is 1.53 to 3.69 times higher for carriers of CYP2C19*2 and CYP2C19*3 compared with non-carriers. [35] A 2020 systematic review and meta-analysis also confirmed that the CYP2C19*2 variant has a strong association with clopidogrel resistance. [34] In 2021 a higher risk of stroke at 90 days was found with clopidogrel than ticagrelor, which does not require metabolic conversion, among Han Chinese CYP2C19 loss-of-function carriers with minor ischemic stroke or TIA. [36]
The following is a table of selected substrates, inducers, and inhibitors of CYP2C19. Where classes of agents are listed, there may be exceptions within the class.
Inhibitors of CYP2C19 can be classified by their potency, such as:
Substrates | Inhibitors | Inducers |
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Omeprazole, sold under the brand names Prilosec and Losec, among others, is a medication used in the treatment of gastroesophageal reflux disease (GERD), peptic ulcer disease, and Zollinger–Ellison syndrome. It is also used to prevent upper gastrointestinal bleeding in people who are at high risk. Omeprazole is a proton-pump inhibitor (PPI) and its effectiveness is similar to that of other PPIs. It can be taken by mouth or by injection into a vein. It is also available in the fixed-dose combination medication omeprazole/sodium bicarbonate as Zegerid and as Konvomep.
Clopidogrel, sold under the brand name Plavix among others, is an antiplatelet medication used to reduce the risk of heart disease and stroke in those at high risk. It is also used together with aspirin in heart attacks and following the placement of a coronary artery stent. It is taken by mouth. Its effect starts about two hours after intake and lasts for five days.
Pharmacogenomics, often abbreviated "PGx," is the study of the role of the genome in drug response. Its name reflects its combining of pharmacology and genomics. Pharmacogenomics analyzes how the genetic makeup of a patient affects their response to drugs. It deals with the influence of acquired and inherited genetic variation on drug response, by correlating DNA mutations with pharmacokinetic, pharmacodynamic, and/or immunogenic endpoints.
Cytochrome P450 3A4 is an important enzyme in the body, mainly found in the liver and in the intestine, which in humans is encoded by CYP3A4 gene. It oxidizes small foreign organic molecules (xenobiotics), such as toxins or drugs, so that they can be removed from the body. It is highly homologous to CYP3A5, another important CYP3A enzyme.
Cytochrome P450 2D6 (CYP2D6) is an enzyme that in humans is encoded by the CYP2D6 gene. CYP2D6 is primarily expressed in the liver. It is also highly expressed in areas of the central nervous system, including the substantia nigra.
Cytochrome P450 2E1 is a member of the cytochrome P450 mixed-function oxidase system, which is involved in the metabolism of xenobiotics in the body. This class of enzymes is divided up into a number of subcategories, including CYP1, CYP2, and CYP3, which as a group are largely responsible for the breakdown of foreign compounds in mammals.
Cytochrome P450 2A6 is a member of the cytochrome P450 mixed-function oxidase system, which is involved in the metabolism of xenobiotics in the body. CYP2A6 is the primary enzyme responsible for the oxidation of nicotine and cotinine. It is also involved in the metabolism of several pharmaceuticals, carcinogens, and a number of coumarin-type alkaloids. CYP2A6 is the only enzyme in the human body that appreciably catalyzes the 7-hydroxylation of coumarin, such that the formation of the product of this reaction, 7-hydroxycoumarin, is used as a probe for CYP2A6 activity.
Cytochrome P450 1A2, a member of the cytochrome P450 mixed-function oxidase system, is involved in the metabolism of xenobiotics in the human body. In humans, the CYP1A2 enzyme is encoded by the CYP1A2 gene.
Cytochrome P450 family 2 subfamily C member 9 is an enzyme protein. The enzyme is involved in the metabolism, by oxidation, of both xenobiotics, including drugs, and endogenous compounds, including fatty acids. In humans, the protein is encoded by the CYP2C9 gene. The gene is highly polymorphic, which affects the efficiency of the metabolism by the enzyme.
Cytochrome P4502C8 (CYP2C8) is a member of the cytochrome P450 mixed-function oxidase system involved in the metabolism of xenobiotics in the body. Cytochrome P4502C8 also possesses epoxygenase activity, i.e. it metabolizes long-chain polyunsaturated fatty acids, e.g. arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and linoleic acid to their biologically active epoxides.
Cytochrome P450, family 1, subfamily A, polypeptide 1 is a protein that in humans is encoded by the CYP1A1 gene. The protein is a member of the cytochrome P450 superfamily of enzymes.
AmpliChip CYP450 Test is a clinical test from Roche and part of the AmpliChip series. The test aims to find the specific gene types ( genotypes) of the patient that will determine how he or she metabolizes certain medicines, and therefore guides the doctors to prescribe the medicine suited for the best effectiveness and least side effects.
Cytochrome P450 2B6 is an enzyme that in humans is encoded by the CYP2B6 gene. CYP2B6 is a member of the cytochrome P450 group of enzymes. Along with CYP2A6, it is involved with metabolizing nicotine, along with many other substances.
Cytochrome P450 3A5 is a protein that in humans is encoded by the CYP3A5 gene.
Cytochrome P450 4A11 is a protein that in humans is codified by the CYP4A11 gene.
Cytochrome P450 4F2 is a protein that in humans is encoded by the CYP4F2 gene. This protein is an enzyme, a type of protein that catalyzes chemical reactions inside cells. This specific enzyme is part of the superfamily of cytochrome P450 (CYP) enzymes, and the encoding gene is part of a cluster of cytochrome P450 genes located on chromosome 19.
Epoxygenases are a set of membrane-bound, heme-containing cytochrome P450 enzymes that metabolize polyunsaturated fatty acids to epoxide products that have a range of biological activities. The most thoroughly studied substrate of the CYP epoxylgenases is arachidonic acid. This polyunsaturated fatty acid is metabolized by cyclooxygenases to various prostaglandin, thromboxane, and prostacyclin metabolites in what has been termed the first pathway of eicosanoid production; it is also metabolized by various lipoxygenases to hydroxyeicosatetraenoic acids and leukotrienes in what has been termed the second pathway of eicosanoid production. The metabolism of arachidonic acid to epoxyeicosatrienoic acids by the CYP epoxygenases has been termed the third pathway of eicosanoid metabolism. Like the first two pathways of eicosanoid production, this third pathway acts as a signaling pathway wherein a set of enzymes metabolize arachidonic acid to a set of products that act as secondary signals to work in activating their parent or nearby cells and thereby orchestrate functional responses. However, none of these three pathways is limited to metabolizing arachidonic acid to eicosanoids. Rather, they also metabolize other polyunsaturated fatty acids to products that are structurally analogous to the eicosanoids but often have different bioactivity profiles. This is particularly true for the CYP epoxygenases which in general act on a broader range of polyunsaturated fatty acids to form a broader range of metabolites than the first and second pathways of eicosanoid production. Furthermore, the latter pathways form metabolites many of which act on cells by binding with and thereby activating specific and well-characterized receptor proteins; no such receptors have been fully characterized for the epoxide metabolites. Finally, there are relatively few metabolite-forming lipoxygenases and cyclooxygenases in the first and second pathways and these oxygenase enzymes share similarity between humans and other mammalian animal models. The third pathway consists of a large number of metabolite-forming CYP epoxygenases and the human epoxygenases have important differences from those of animal models. Partly because of these differences, it has been difficult to define clear roles for the epoxygenase-epoxide pathways in human physiology and pathology.
Adenosine diphosphate (ADP) receptor inhibitors are a drug class of antiplatelet agents, used in the treatment of acute coronary syndrome (ACS) or in preventive treatment for patients who are in risk of thromboembolism, myocardial infarction or a stroke. These drugs antagonize the P2Y12 platelet receptors and therefore prevent the binding of ADP to the P2Y12 receptor. This leads to a decrease in aggregation of platelets, prohibiting thrombus formation. The P2Y12 receptor is a surface bound protein found on blood platelets. They belong to G protein-coupled purinergic receptors (GPCR) and are chemoreceptors for ADP.
20-Hydroxyeicosatetraenoic acid, also known as 20-HETE or 20-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid, is an eicosanoid metabolite of arachidonic acid that has a wide range of effects on the vascular system including the regulation of vascular tone, blood flow to specific organs, sodium and fluid transport in the kidney, and vascular pathway remodeling. These vascular and kidney effects of 20-HETE have been shown to be responsible for regulating blood pressure and blood flow to specific organs in rodents; genetic and preclinical studies suggest that 20-HETE may similarly regulate blood pressure and contribute to the development of stroke and heart attacks. Additionally the loss of its production appears to be one cause of the human neurological disease, Hereditary spastic paraplegia. Preclinical studies also suggest that the overproduction of 20-HETE may contribute to the progression of certain human cancers, particularly those of the breast.
In biochemistry, cytochrome P450 enzymes have been identified in all kingdoms of life: animals, plants, fungi, protists, bacteria, and archaea, as well as in viruses. As of 2018, more than 300,000 distinct CYP proteins are known.
This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This protein localizes to the endoplasmic reticulum and is known to metabolize many xenobiotics, including the anticonvulsive drug mephenytoin, omeprazole, diazepam and some barbiturates. Polymorphism within this gene is associated with variable ability to metabolize mephenytoin, known as the poor metabolizer and extensive metabolizer phenotypes. The gene is located within a cluster of cytochrome P450 genes on chromosome 10q24.This article incorporates text from this source, which is in the public domain .
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