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Available structures
PDBOrtholog search: PDBe RCSB
AliasesCYP1A1, AHH, AHRR, CP11, CYP1, P1-450, P450-C, P450DX, CYPIA1, cytochrome P450 family 1 subfamily A member 1
External IDsOMIM: 108330 MGI: 88588 HomoloGene: 68062 GeneCards: CYP1A1
Gene location (Human)
Chromosome 15 (human)
Chr.Chromosome 15 (human)[1]
Chromosome 15 (human)
Genomic location for CYP1A1
Genomic location for CYP1A1
Band15q24.1Start74,719,542 bp[1]
End74,725,536 bp[1]
RNA expression pattern
PBB GE CYP1A1 205749 at fs.png
More reference expression data
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 15: 74.72 – 74.73 MbChr 9: 57.69 – 57.7 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Cytochrome P450, family 1, subfamily A, polypeptide 1 is a protein[5] that in humans is encoded by the CYP1A1 gene.[6] The protein is a member of the cytochrome P450 superfamily of enzymes.[7]


Metabolism of xenobiotics and drugs[edit]

CYP1A1 is involved in phase I xenobiotic and drug metabolism (one substrate of it is theophylline). It is inhibited by hesperetin (a flavonoid found in lime, sweet orange),[8] fluoroquinolones and macrolides and induced by aromatic hydrocarbons.[9]

CYP1A1 is also known as AHH (aryl hydrocarbon hydroxylase). It is involved in the metabolic activation of aromatic hydrocarbons (polycyclic aromatic hydrocarbons, PAH), for example, benzo[a]pyrene (BaP), by transforming it to an epoxide. In this reaction, the oxidation of benzo[a]pyrene is catalysed by CYP1A1 to form BaP-7,8-epoxide, which can be further oxidized by epoxide hydrolase (EH) to form BaP-7,8-dihydrodiol. Finally, CYP1A1 catalyses this intermediate to form BaP-7,8-dihydrodiol-9,10-epoxide, which is a carcinogen.[9]

However, an in vivo experiment with gene-deficient mice has found that the hydroxylation of benzo[a]pyrene by CYP1A1 can have an overall protective effect on the DNA, rather than contributing to potentially carcinogenic DNA modifications. This effect is likely due to the fact that CYP1A1 is highly active in the intestinal mucosa, and thus inhibits infiltration of ingested benzo[a]pyrene carcinogen into the systemic circulation.[10]

CYP1A1 metabolism of various foreign agents to carcinogens has been implicated in the formation of various types of human cancer.[11][12]

Metabolism of endogenous agents[edit]

CYP1A1 also metabolizes polyunsaturated fatty acids into signaling molecules that have physiological as well as pathological activities. CYP1A1 has monoxygenase activity in that it metabolizes arachidonic acid to 19-hydroxyeicosatetraenoic acid (19-HETE) (see 20-Hydroxyeicosatetraenoic acid) but also has epoxygenase activity in that it metabolizes docosahexaenoic acid to epoxides, primarily 19R,20S-epoxyeicosapentaenoic acid and 19S,20R-epoxyeicosapentaenoic acid isomers (termed 19,20-EDP) and similarly metabolizes eicosapentaenoic acid to epoxides, primarily 17R,18S-eicosatetraenic acid and 17S,18R-eicosatetraenic acid isomers (termed 17,18-EEQ).[13] Synthesis of 12(S)-HETE by CYP1A1 has also been demonstrated.[14] 19-HETE is an inhibitor of 20-HETE, a broadly active signaling molecule, e.g. it constricts arterioles, elevates blood pressure, promotes inflammation responses, and stimulates the growth of various types of tumor cells; however the in vivo ability and significance of 19-HETE in inhibiting 20-HETE has not been demonstrated (see 20-Hydroxyeicosatetraenoic acid).

The EDP (see Epoxydocosapentaenoic acid) and EEQ (see epoxyeicosatetraenoic acid) metabolites have a broad range of activities. In various animal models and in vitro studies on animal and human tissues, they decrease hypertension and pain perception; suppress inflammation; inhibit angiogenesis, endothelial cell migration and endothelial cell proliferation; and inhibit the growth and metastasis of human breast and prostate cancer cell lines.[15][16][17][18] It is suggested that the EDP and EEQ metabolites function in humans as they do in animal models and that, as products of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid, the EDP and EEQ metabolites contribute to many of the beneficial effects attributed to dietary omega-3 fatty acids.[15][18][19] EDP and EEQ metabolites are short-lived, being inactivated within seconds or minutes of formation by epoxide hydrolases, particularly soluble epoxide hydrolase, and therefore act locally. CYP1A1 is one of the main extra-hepatic cytochrome P450 enzymes; it is not regarded as being a major contributor to forming the cited epoxides[18] but could act locally in certain tissues such as the intestine and in certain cancers to do so.


The expression of the CYP1A1 gene, along with that of CYP1A2/1B1 genes, is regulated by a heterodimeric transcription factor that consist of the aryl hydrocarbon receptor, a ligand activated transcription factor, and the aryl hydrocarbon receptor nuclear translocator.[20] In the intestine, but not the liver, CYP1A1 expression moreover depends on TOLL-like receptor 2 (TLR2),[21] which recognizes bacterial surface structures such as lipoteichoic acid. Additionally, the tumour suppressor p53 has been shown to impact CYP1A1 expression thereby modulating the metabolic activation of several environmental carcinogens such as PAHs.[22]


Several polymorphisms have been identified in CYP1A1, some of which lead to more highly inducible AHH activity. CYP1A1 polymorphisms include:[23][24][25][26]

  • M1, TC substitution at nucleotide 3801 in the 3'-non-coding region
  • M2, AG substitution at nucleotide 2455 leading to an amino acid change of isoleucine to valine at codon 462
  • M3, TC substitution at nucleotide 3205 in the 3'-non-coding region
  • M4, CA substitution at nucleotide 2453 leading to an amino acid change of threonine to asparagine at codon 461

The highly inducible forms of CYP1A1 are associated with an increased risk of lung cancer in smokers. (Reference = Kellerman et al., New Eng J Med 1973:289;934-937) Light smokers with the susceptible genotype CYP1A1 have a sevenfold higher risk of developing lung cancer compared to light smokers with the normal genotype.


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000140465 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000032315 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ Kawajiri K (1999). "CYP1A1". IARC Scientific Publications (148): 159–72. PMID 10493257.
  6. ^ Nelson DR, Zeldin DC, Hoffman SM, Maltais LJ, Wain HM, Nebert DW (Jan 2004). "Comparison of cytochrome P450 (CYP) genes from the mouse and human genomes, including nomenclature recommendations for genes, pseudogenes and alternative-splice variants". Pharmacogenetics. 14 (1): 1–18. doi:10.1097/00008571-200401000-00001. PMID 15128046.
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  8. ^ Briguglio, M.; Hrelia, S.; Malaguti, M.; Serpe, L.; Canaparo, R.; Dell'Osso, B.; Galentino, R.; De Michele, S.; Dina, C. Z.; Porta, M.; Banfi, G. (2018). "Food Bioactive Compounds and Their Interference in Drug Pharmacokinetic/Pharmacodynamic Profiles". Pharmaceutics. 10 (4): 277. doi:10.3390/pharmaceutics10040277. PMC 6321138. PMID 30558213.
  9. ^ a b Beresford AP (1993). "CYP1A1: friend or foe?". Drug Metabolism Reviews. 25 (4): 503–17. doi:10.3109/03602539308993984. PMID 8313840.
  10. ^ Uno S, Dalton TP, Derkenne S, Curran CP, Miller ML, Shertzer HG, Nebert DW (May 2004). "Oral exposure to benzo[a]pyrene in the mouse: detoxication by inducible cytochrome P450 is more important than metabolic activation". Molecular Pharmacology. 65 (5): 1225–37. doi:10.1124/mol.65.5.1225. PMID 15102951.
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  15. ^ a b Fleming I (Oct 2014). "The pharmacology of the cytochrome P450 epoxygenase/soluble epoxide hydrolase axis in the vasculature and cardiovascular disease". Pharmacological Reviews. 66 (4): 1106–40. doi:10.1124/pr.113.007781. PMID 25244930.
  16. ^ Zhang G, Kodani S, Hammock BD (Jan 2014). "Stabilized epoxygenated fatty acids regulate inflammation, pain, angiogenesis and cancer". Progress in Lipid Research. 53: 108–23. doi:10.1016/j.plipres.2013.11.003. PMC 3914417. PMID 24345640.
  17. ^ He J, Wang C, Zhu Y, Ai D (Dec 2015). "Soluble epoxide hydrolase: A potential target for metabolic diseases". Journal of Diabetes. 8 (3): 305–13. doi:10.1111/1753-0407.12358. PMID 26621325.
  18. ^ a b c Wagner K, Vito S, Inceoglu B, Hammock BD (Oct 2014). "The role of long chain fatty acids and their epoxide metabolites in nociceptive signaling". Prostaglandins & Other Lipid Mediators. 113–115: 2–12. doi:10.1016/j.prostaglandins.2014.09.001. PMC 4254344. PMID 25240260.
  19. ^ Fischer R, Konkel A, Mehling H, Blossey K, Gapelyuk A, Wessel N, von Schacky C, Dechend R, Muller DN, Rothe M, Luft FC, Weylandt K, Schunck WH (Mar 2014). "Dietary omega-3 fatty acids modulate the eicosanoid profile in man primarily via the CYP-epoxygenase pathway". Journal of Lipid Research. 55 (6): 1150–1164. doi:10.1194/jlr.M047357. PMC 4031946. PMID 24634501.
  20. ^ Ma Q, Lu AY (Jul 2007). "CYP1A induction and human risk assessment: an evolving tale of in vitro and in vivo studies". Drug Metabolism and Disposition. 35 (7): 1009–16. doi:10.1124/dmd.107.015826. PMID 17431034. S2CID 7512239.
  21. ^ Do KN, Fink LN, Jensen TE, Gautier L, Parlesak A (2012). "TLR2 controls intestinal carcinogen detoxication by CYP1A1". PLOS ONE. 7 (3): e32309. Bibcode:2012PLoSO...732309D. doi:10.1371/journal.pone.0032309. PMC 3307708. PMID 22442665.
  22. ^ Wohak, L.E.; Krais, A.M.; Kucab, J.E.; Stertmann, J.; Ovrebo, S.; Phillips, D.H.; Arlt, V.M. (2016). "Carcinogenic polycyclic aromatic hydrocarbons induce CYP1A1 in human cells via a p53-dependent mechanism". Arch Toxicol. 90 (2): 291–304. doi:10.1007/s00204-014-1409-1. PMC 4748000. PMID 25398514.
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Further reading[edit]