|Cytochrome P450, family 3, subfamily A, polypeptide 4|
|Symbols||; CP33; CP34; CYP3A; CYP3A3; CYPIIIA3; CYPIIIA4; HLP; NF-25; P450C3; P450PCN1|
|RNA expression pattern|
Cytochrome P450 3A4 (abbreviated CYP3A4) (EC 22.214.171.124), is an important enzyme in the body, mainly found in the liver and in the intestine. Its purpose is to oxidize small foreign organic molecules (xenobiotics), such as toxins or drugs, so that they can be removed from the body.
While many drugs are deactivated by CYP3A4, there are also some drugs which are activated by the enzyme. Some substances, such as grapefruit juice and some drugs, interfere with the action of CYP3A4. These substances will therefore either amplify or weaken the action of those drugs that are modified by CYP3A4.
CYP3A4 is a member of the cytochrome P450 family of oxidizing enzymes. Several other members of this family are also involved in drug metabolism, but CYP3A4 is the most common and the most versatile one. Like all members of this family, it is a hemoprotein, i.e. a protein containing a heme group with an iron atom. In humans, the CYP3A4 protein is encoded by the CYP3A4 gene. This gene is part of a cluster of cytochrome P450 genes on chromosome 7q21.1.
CYP3A4 is a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids, and other lipids components.
The CYP3A4 protein localizes to the endoplasmic reticulum, and its expression is induced by glucocorticoids and some pharmacological agents. This enzyme is involved in the metabolism of approximately half the drugs that are used today, including acetaminophen, codeine, ciclosporin (cyclosporin), diazepam, and erythromycin. The enzyme also metabolizes some steroids and carcinogens. Most drugs undergo deactivation by CYP3A4, either directly or by facilitated excretion from the body. Also, many substances are bioactivated by CYP3A4 to form their active compounds, and many protoxins being toxicated into their toxic forms (for examples - see table below).
The CYP3A4 gene exhibits a much more complicated upstream regulatory region in comparison with its paralogs. This increased complexity renders the CYP3A4 gene more sensitive to endogenous and exogenous PXR and CAR ligands, instead of relying on gene variants for wider specificity. Chimpanzee and human CYP3A4 are highly conserved in metabolism of many ligands, although four amino acids positively selected in humans led to a 5-fold benzylation of 7-BFC in the presence of the hepatotoxic secondary bile acid lithocholic acid. This change in consequence contributes to an increased human defense against cholestasis.
Fetuses do not really express CYP3A4 in their liver tissue, but rather CYP3A7 (EC 126.96.36.199), which acts on a similar range of substrates. CYP3A4 is absent in fetal liver but increases to approximately 40% of adult levels in the fourth month of life and 72% at 12 months.
Although CYP3A4 is predominantly found in the liver, it is also present in other organs and tissues of the body, where it may play an important role in metabolism. CYP3A4 in the intestine plays an important role in the metabolism of certain drugs. Often this allows prodrugs to be activated and absorbed - as in the case of the histamine H1-receptor antagonist terfenadine.
Cytochrome P450 enzymes perform an assortment of modifications on a variety of ligands, utilizing its large active site and its ability to bind more than one substrate at a time to perform complicated chemical alterations in the metabolism of endogenous and exogenous compounds. These include hydroxylation, epoxidation of olefins, aromatic oxidation, heteroatom oxidations, N- and O- dealkylation reactions, aldehyde oxidations, dehydrogenation reactions, and aromatase activity.
Hydroxylation of an sp3 C-H bond is one of the ways in which CYP3A4 (and cytochrome P450 oxygenases) affects its ligand. In fact, hydroxylation is sometimes followed by dehydrogenation, leading to more complex metabolites. An example of a molecule that undergoes more than one reaction due to CYP3A4 includes tamoxifen, which is hydroxylated to 4-hydroxy-tamoxifen and then dehydrated to 4-hydroxy-tamoxifen quinone methide. Two mechanisms have been proposed as the primary pathway of hydroxylation in P450 enzymes.
The first pathway suggested is a cage-controlled radical method (“oxygen rebound”), and the second involves a concerted mechanism that does not utilize a radical intermediate but instead acts very quickly via a “radical clock”.
Inhibition through fruit ingestion
In 1998, various researchers showed that grapefruit juice, and grapefruit in general, is a potent inhibitor of CYP3A4, which can affect the metabolism of a variety of drugs, increasing their bioavailability. In some cases, this can lead to a fatal interaction with drugs like astemizole or terfenadine. The effect of grapefruit juice with regard to drug absorption was originally discovered in 1989. The first published report on grapefruit drug interactions was in 1991 in the Lancet entitled "Interactions of Citrus Juices with Felodipine and Nifedipine" and was the first reported food-drug interaction clinically. However, the effect became well-publicized after being responsible for a number of deaths due to overdosing on medication.[dubious ] The effects of grapefruit last from 3–7 days, with the greatest effects when taken simultaneously with the drug.
In addition to grapefruit, other fruits have similar effects. Noni (M. citrifolia), for example, is a dietary supplement typically consumed as a juice and also inhibits CYP3A4; pomegranate juice has this effect as well.
While over 28 single nucleotide polymorphisms (SNPs) have been identified in the CYP3A4 gene, it has been found that this does not translate into significant interindividual variability in vivo. It can be supposed that this may be due to the induction of CYP3A4 on exposure to substrates.
CYP3A4 alleles which have been reported to have minimal function compared to wild-type include CYP3A4*6 (an A17776 insertion) and CYP3A4*17 (F189S). Both of these SNPs led to decreased catalytic activity with certain ligands, including testosterone and nifedipine in comparison to wild-type metabolism.
Variability in CYP3A4 function can be determined noninvasively by the erythromycin breath test (ERMBT). The ERMBT estimates in vivo CYP3A4 activity by measuring the radiolabelled carbon dioxide exhaled after an intravenous dose of (14C-N-methyl)-erythromycin.
CYP3A4 is induced by a wide variety of ligands. These ligands bind to the pregnane X receptor (PXR). The activated PXR complex forms a heterodimer with the retinoid X receptor (RXR), which binds to the XREM region of the CYP3A4 gene. XREM is a regulatory region of the CYP3A4 gene, and binding causes a cooperative interaction with proximal promoter regions of the gene, resulting in increased transcription and expression of CYP3A4. Activation of the PXR/RXR heterodimer initiates transcription of the CYP3A4 promoter region and gene. Ligand binding increases when in the presence of CYP3A4 ligands, such as in the presence of alfatoxins B1, M1, and G1. Indeed, due to the enzyme’s large and malleable active site, it is possible for the enzyme to bind multiple ligands at once, leading to potentially detrimental side effects.
Induction of CYP3A4 has been shown to vary in humans depending on gender. Evidence shows an increased drug clearance by CYP3A4 in women, even when accounting for differences in body weight. A study by Wobold et al. (2003) found that the median CYP3A4 levels measured from surgically removed liver samples of a random sample of women exceeded CYP3A4 levels in the livers of men by 129%. CYP3A4 mRNA transcripts were found in similar proportions, suggesting a pre-translational mechanism for the up-regulation of CYP3A4 in women. The exact cause of this elevated level of enzyme in women is still under speculation, however studies have elucidated other mechanisms (such as CYP3A5 or CYP3A7 compensation for lowered levels of CYP3A4) that affect drug clearance in both men and women.
CYP3A4 substrate activation varies amongst different animal species. Certain ligands activate human PXR, which promotes CYP3A4 transcription, while showing no activation in other species. For instance, mouse PXR is not activated by rifampicin and human PXR is not activated by pregnenalone 16α-carbonitrile In order to facilitate study of CYP3A4 functional pathways in vivo, mouse strains have been developed using transgenes in order to produce null/human CYP3A4 and PXR crosses. Although humanized hCYP3A4 mice successfully expressed the enzyme in their intestinal tract, low levels of hCYP3A4 were found in the liver. This effect has been attributed to CYP3A4 regulation by the growth hormone signal transduction pathway. In addition to providing an in vivo model, humanized CYP3A4 mice (hCYP3A4) have been used to further emphasize gender differences in CYP3A4 activity.
CYP3A4 activity levels have also been linked to diet and environmental factors, such as duration of exposure to xenobiotic substances. Due to the enzyme’s extensive presence in the intestinal mucosa, the enzyme has shown sensitivity to starvation symptoms and is upregulated in defense of adverse effects. Indeed, in fatheaded minnows, unfed female fish were shown to have increased PXR and CYP3A4 expression, and displayed a more pronounced response to xenobiotic factors after exposure after several days of starvation. By studying animal models and keeping in mind the innate differences in CYP3A4 activation, investigators can better predict drug metabolism and side effects in human CYP3A4 pathways.
Estimates of the turnover rate of human CYP3A4 vary widely. For hepatic CYP3A4, in vivo methods yield estimates of enzyme half-life mainly in the range of 70 to 140 hours, whereas in vitro methods give estimates from 26 to 79 hours. Turnover of gut CYP3A4 is likely to be a function of the rate of enterocyte renewal; an indirect approach based on recovery of activity following exposure to grapefruit juice yields measurements in the 12 to 33 hour range.
Due to membrane-bound CYP3A4’s natural propensity to conglomerate, it has historically been difficult to study drug binding in both solution and on surfaces. Co-crystallization is difficult since the substrates tend to have a low Kd (between 5-150 μM) and low solubility in aqueous solutions. A successful strategy in isolating the bound enzyme is the functional stabilization of monomeric CYP3A4 on Ag nanoparticles produced from nanosphere lithography and analyzed via localized surface plasmon resonance spectroscopy (LSPR). These analyses can be used as a high-sensitivity assay of drug binding, and may become integral in further high-throughput assays utilized in initial drug discovery testing. In addition to LSPR, CYP3A4-Nanodisc complexes have been found helpful in other applications including solid-state NMR, redox potentiometry, and steady-state enzyme kinetics.
Inhibitors of CYP3A4 can be classified by their potency, such as:
- Strong inhibitor being one that causes at least a 5-fold increase in the plasma AUC values, or more than 80% decrease in clearance.
- Moderate inhibitor being one that causes at least a 2-fold increase in the plasma AUC values, or 50-80% decrease in clearance.
- Weak inhibitor being one that causes at least a 1.25-fold but less than 2-fold increase in the plasma AUC values, or 20-50% decrease in clearance.
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles. [§ 1]
- The interactive pathway map can be edited at WikiPathways: "IrinotecanPathway_WP46359".
- Hashimoto H, Toide K, Kitamura R, Fujita M, Tagawa S, Itoh S, Kamataki T (December 1993). "Gene structure of CYP3A4, an adult-specific form of cytochrome P450 in human livers, and its transcriptional control". Eur. J. Biochem. 218 (2): 585–95. doi:10.1111/j.1432-1033.1993.tb18412.x. PMID 8269949.
- Inoue K, Inazawa J, Nakagawa H, Shimada T, Yamazaki H, Guengerich FP, Abe T (June 1992). "Assignment of the human cytochrome P-450 nifedipine oxidase gene (CYP3A4) to chromosome 7 at band q22.1 by fluorescence in situ hybridization". Jpn. J. Hum. Genet. 37 (2): 133–8. doi:10.1007/BF01899734. PMID 1391968.
- "Entrez Gene: cytochrome P450".
- Qiu H, Mathäs M, Nestler S, Bengel C, Nem D, Gödtel-Armbrust U, Lang T, Taudien S, Burk O, Wojnowski L (March 2010). "The unique complexity of the CYP3A4 upstream region suggests a nongenetic explanation of its expression variability". Pharmacogenet. Genomics 20 (3): 167–78. doi:10.1097/FPC.0b013e328336bbeb. PMID 20147837.
- Kumar S, Qiu H, Oezguen N, Herlyn H, Halpert JR, Wojnowski L (June 2009). "Ligand diversity of human and chimpanzee CYP3A4: activation of human CYP3A4 by lithocholic acid results from positive selection". Drug Metab. Dispos. 37 (6): 1328–33. doi:10.1124/dmd.108.024372. PMC 2683693. PMID 19299527.
- Johnson TN, Rostami-Hodjegan A, Tucker GT (2006). "Prediction of the clearance of eleven drugs and associated variability in neonates, infants and children". Clin Pharmacokinet 45 (9): 931–56. doi:10.2165/00003088-200645090-00005. PMID 16928154.
- Johnson TN, Tucker GT, Rostami-Hodjegan A (May 2008). "Development of CYP2D6 and CYP3A4 in the first year of life". Clin. Pharmacol. Ther. 83 (5): 670–1. doi:10.1038/sj.clpt.6100327. PMID 18043691.
- Robertson G, Field J, Goodwin B, Bierach S, Tran M, Lehnert A, Liddle C (2003). "Transgenic mouse models of human CYP3A4 gene regulation". Mol Pharmacol 64 (1): 42–50. doi:10.1124/mol.64.1.42. PMID 12815159.
- Schmiedlin-Ren P, Edwards DJ, Fitzsimmons ME, He K, Lown KS, Woster PM, Rahman A, Thummel KE, Fisher JM, Hollenberg PF, Watkins PB (November 1997). "Mechanisms of enhanced oral availability of CYP3A4 substrates by grapefruit constituents. Decreased enterocyte CYP3A4 concentration and mechanism-based inactivation by furanocoumarins". Drug Metab. Dispos. 25 (11): 1228–33. PMID 9351897.
- Shahrokh K, Cheatham TE, Yost GS (October 2012). "Conformational dynamics of CYP3A4 demonstrate the important role of Arg212 coupled with the opening of ingress, egress and solvent channels to dehydrogenation of 4-hydroxy-tamoxifen". Biochim. Biophys. Acta 1820 (10): 1605–17. doi:10.1016/j.bbagen.2012.05.011. PMID 22677141.
- Meunier B, de Visser SP, Shaik S (September 2004). "Mechanism of oxidation reactions catalyzed by cytochrome p450 enzymes". Chem. Rev. 104 (9): 3947–80. doi:10.1021/cr020443g. PMID 15352783.
- He K, Iyer KR, Hayes RN, Sinz MW, Woolf TF, Hollenberg PF (April 1998). "Inactivation of cytochrome P450 3A4 by bergamottin, a component of grapefruit juice". Chemical Research in Toxicology 11 (4): 252–9. doi:10.1021/tx970192k. PMID 9548795.
- Bailey DG, Malcolm J, Arnold O, Spence JD (August 1998). "Grapefruit juice–drug interactions". British Journal of Clinical Pharmacology 46 (2): 101–10. doi:10.1046/j.1365-2125.1998.00764.x. PMC 1873672. PMID 9723817.
- Garg SK, Kumar N, Bhargava VK, Prabhakar SK (September 1998). "Effect of grapefruit juice on carbamazepine bioavailability in patients with epilepsy". Clinical Pharmacology and Therapeutics 64 (3): 286–8. doi:10.1016/S0009-9236(98)90177-1. PMID 9757152.
- Bailey DG, Dresser GK (2004). "Interactions between grapefruit juice and cardiovascular drugs". American Journal of Cardiovascular Drugs 4 (5): 281–97. doi:10.2165/00129784-200404050-00002. PMID 15449971.
- Bressler R (November 2006). "Grapefruit juice and drug interactions. Exploring mechanisms of this interaction and potential toxicity for certain drugs". Geriatrics 61 (11): 12–8. PMID 17112309.
- Lilja JJ, Kivistö KT, Neuvonen PJ. Duration of effect of grapefruit juice on the pharmacokinetics of the CYP3A4 substrate simvastatin. Clin Pharmacol Ther. 2000 Oct;68(4):384-90. PMID 11061578 
- "Integrative Medicine, Noni". Memorial Sloan-Kettering Cancer Center. Retrieved 2013-06-27.
- Hidaka M, Okumura M, Fujita K, Ogikubo T, Yamasaki K, Irakiri T, Setoguchi N, Amimori K (2005). "Effects of pomegranate juice on human cytochrome P450 3A (CYP3A) and carbamazepine pharmaknkinetics in rats". Drug Metabolism & Dispositon 33 (5): 644–8. doi:10.1124/dmd.104.002824.
- Lee SJ, Goldstein JA (June 2005). "Functionally defective or altered CYP3A4 and CYP3A5 single nucleotide polymorphisms and their detection with genotyping tests". Pharmacogenomics 6 (4): 357–71. doi:10.1517/146224188.8.131.527. PMID 16004554.
- Watkins PB (August 1994). "Noninvasive tests of CYP3A enzymes". Pharmacogenetics 4 (4): 171–84. doi:10.1097/00008571-199408000-00001. PMID 7987401.
- Ratajewski M, Walczak-Drzewiecka A, Sałkowska A, Dastych J (August 2011). "Aflatoxins upregulate CYP3A4 mRNA expression in a process that involves the PXR transcription factor". Toxicol. Lett. 205 (2): 146–53. doi:10.1016/j.toxlet.2011.05.1034. PMID 21641981.
- Wolbold R, Klein K, Burk O, Nüssler AK, Neuhaus P, Eichelbaum M, Schwab M, Zanger UM (October 2003). "Sex is a major determinant of CYP3A4 expression in human liver". Hepatology 38 (4): 978–88. doi:10.1053/jhep.2003.50393. PMID 14512885.
- Gonzalez FJ (2007). "CYP3A4 and pregnane X receptor humanized mice". J. Biochem. Mol. Toxicol. 21 (4): 158–62. doi:10.1002/jbt.20173. PMID 17936928.
- Crago J, Klaper RD (September 2011). "Influence of gender, feeding regimen, and exposure duration on gene expression associated with xenobiotic metabolism in fathead minnows (Pimephales promelas)". Comp. Biochem. Physiol. C Toxicol. Pharmacol. 154 (3): 208–12. doi:10.1016/j.cbpc.2011.05.016. PMID 21664292.
- Yang, J.; Liao, M.; Shou, M.; Jamei, M.; Yeo, K. R.; Tucker, G. T.; Rostami-Hodjegan, A. (2008-06-01). "Cytochrome P450 turnover: regulation of synthesis and degradation, methods for determining rates, and implications for the prediction of drug interactions". Current Drug Metabolism (Bentham) 9 (5): 384–393. doi:10.2174/138920008784746382. PMID 18537575. Retrieved 2010-12-20.
- Sevrioukova IF, Poulos TL (January 2012). "Structural and mechanistic insights into the interaction of cytochrome P4503A4 with bromoergocryptine, a type I ligand". J. Biol. Chem. 287 (5): 3510–7. doi:10.1074/jbc.M111.317081. PMC 3271004. PMID 22157006.
- Das A, Zhao J, Schatz GC, Sligar SG, Van Duyne RP (May 2009). "Screening of type I and II drug binding to human cytochrome P450-3A4 in nanodiscs by localized surface plasmon resonance spectroscopy". Anal. Chem. 81 (10): 3754–9. doi:10.1021/ac802612z. PMID 19364136.
- Flockhart DA (2007). "Drug Interactions: Cytochrome P450 Drug Interaction Table". Indiana University School of Medicine. Retrieved on December 25, 2008.
- Where classes of agents are listed, there may be exceptions within the class
- FASS (drug formulary): Swedish environmental classification of pharmaceuticals Facts for prescribers (Fakta för förskrivare). Retrieved July 2011
Metabolized primarily by CYP3A4 and, to a lesser degree, by CYP1A2 and the extrahepatic isoform CYP1A1
- "Cyclobenzaprine". DrugBank.
- Moody DE, Fang WB, Lin SN, Weyant DM, Strom SC, Omiecinski CJ (December 2009). "Effect of rifampin and nelfinavir on the metabolism of methadone and buprenorphine in primary cultures of human hepatocytes". Drug Metab. Dispos. 37 (12): 2323–9. doi:10.1124/dmd.109.028605. PMC 2784702. PMID 19773542.
- Cockshott ID (2004). "Bicalutamide: clinical pharmacokinetics and metabolism". Clin Pharmacokinet 43 (13): 855–78. doi:10.2165/00003088-200443130-00003. PMID 15509184.
- Matsumoto S, Yamazoe Y (February 2001). "Involvement of multiple human cytochromes P450 in the liver microsomal metabolism of astemizole and a comparison with terfenadine". British Journal of Clinical Pharmacology 51 (2): 133–42. doi:10.1046/j.1365-2125.2001.01292.x. PMC 2014443. PMID 11259984.
- Daly AK, King BP (May 2003). "Pharmacogenetics of oral anticoagulants". Pharmacogenetics 13 (5): 247–52. doi:10.1097/01.fpc.0000054071.64000.bd. PMID 12724615.
- Lau WC, Waskell LA, Watkins PB, Neer CJ, Horowitz K, Hopp AS, Tait AR, Carville DG, Guyer KE, Bates ER (January 2003). "Atorvastatin reduces the ability of clopidogrel to inhibit platelet aggregation: a new drug-drug interaction". Circulation 107 (1): 32–7. doi:10.1161/01.CIR.0000047060.60595.CC. PMID 12515739.
- Meyer MR, Bach M, Welter J, Bovens M, Turcant A, Maurer HH (2013). "Ketamine-derived designer drug methoxetamine: metabolism including isoenzyme kinetics and toxicological detectability using GC-MS and LC-(HR-)MSn". Anal Bioanal Chem 405 (19): 6307–21. doi:10.1007/s00216-013-7051-6. PMID 23774830.
- Rod Flower; Humphrey P. Rang; Maureen M. Dale; Ritter, James M. (2007). Rang & Dale's pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-06911-5.
- Park JY, Kim KA, Kim SL (November 2003). "Chloramphenicol Is a Potent Inhibitor of Cytochrome P450 Isoforms CYP2C19 and CYP3A4 in Human Liver Microsomes". Antimicrob. Agents Chemother. 47 (11): 3464–9. doi:10.1128/AAC.47.11.3464-3469.2003. PMC 253795. PMID 14576103.
- Zhang W, Ramamoorthy Y, Tyndale RF, Sellers EM (June 2003). "Interaction of buprenorphine and its metabolite norbuprenorphine with cytochromes P450 in vitro". Drug Metab. Dispos. 31 (6): 768–72. doi:10.1124/dmd.31.6.768. PMID 12756210.
- Non-nucleoside reverse transcriptase inhibitors have been shown to both induce and inhibit CYP3A4.
- Hidaka M, Fujita K, Ogikubo T, et al. (June 2004). "Potent inhibition by star fruit of human cytochrome P450 3A (CYP3A) activity". Drug Metab. Dispos. 32 (6): 581–3. doi:10.1124/dmd.32.6.581. PMID 15155547.
- Kimura Y, Ito H, Ohnishi R, Hatano T (January 2010). "Inhibitory effects of polyphenols on human cytochrome P450 3A4 and 2C9 activity". Food Chem. Toxicol. 48 (1): 429–35. doi:10.1016/j.fct.2009.10.041. PMID 19883715.
Ginko Biloba has been shown to contain the potent inhibitor amentoflavone
- Bhardwaj RK, Glaeser H, Becquemont L, Klotz U, Gupta SK, Fromm MF (August 2002). "Piperine, a major constituent of black pepper, inhibits human P-glycoprotein and CYP3A4". J. Pharmacol. Exp. Ther. 302 (2): 645–50. doi:10.1124/jpet.102.034728. PMID 12130727.
- Wen X, Wang JS, Neuvonen PJ, Backman JT. "Isoniazid is a mechanism-based inhibitor of cytochrome P450 1A2, 2A6, 2C19 and 3A4 isoforms in human liver microsomes.". PMID 11868802.