Английская Википедия:CYP3A4

Материал из Онлайн справочника
Перейти к навигацииПерейти к поиску

Шаблон:Short description Шаблон:Use dmy dates Шаблон:Cs1 config Шаблон:Use American English Шаблон:Infobox enzymeШаблон:Infobox gene Cytochrome P450 3A4 (abbreviated CYP3A4) (Шаблон:EC number) 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.

While many drugs are deactivated by CYP3A4, there are also some drugs that are activated by the enzyme. Some substances, such as some drugs and furanocoumarins present in grapefruit juice, 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.[1] This gene is part of a cluster of cytochrome P450 genes on chromosome 7q22.1.[2] Previously another CYP3A gene, CYP3A3, was thought to exist; however, it is now thought that this sequence represents a transcript variant of CYP3A4. Alternatively-spliced transcript variants encoding different isoforms have been identified.[3]

Function

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 steroids (including cholesterol), and other lipids.[3]

The CYP3A4 protein localizes to the endoplasmic reticulum, and its expression is induced by glucocorticoids and some pharmacological agents.[3] Cytochrome P450 enzymes metabolize approximately 60% of prescribed drugs, with CYP3A4 responsible for about half of this metabolism;[4] substrates include acetaminophen (paracetamol), codeine, ciclosporin (cyclosporin), diazepam, erythromycin, and chloroquine.[3] The enzyme also metabolizes some steroids and carcinogens.[5] 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 are toxicated into their toxic forms (see table below for examples).

CYP3A4 also possesses epoxygenase activity in that it metabolizes arachidonic acid to epoxyeicosatrienoic acids (EETs), i.e. (±)-8,9-, (±)-11,12-, and (±)-14,15-epoxyeicosatrienoic acids.[6] EETs have a wide range of activities including the promotion of certain types of cancers (see epoxyeicosatetraenoic acid). CYP3A4 promotes the growth of various types of human cancer cell lines in culture by producing (±)-14,15-epoxyeicosatrienoic acids, which stimulate these cells to grow.[7] The CYP3A4 enzyme is also reported to have fatty acid monooxgenase activity for metabolizing arachidonic acid to 20-Hydroxyeicosatetraenoic acid (20-HETE).[8] 20-HETE has a wide range of activities that include growth stimulation in breast and other types of cancers (see 12-hydroxyeicosatetraenoic acid).

Evolution

The CYP3A4 gene exhibits a much more complicated upstream regulatory region in comparison with its paralogs.[9] 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.[9] 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.[10] This change in consequence contributes to an increased human defense against cholestasis.[10]

Tissue distribution

Fetuses do not express CYP3A4 in their liver tissue, but rather CYP3A7 (Шаблон:EC number), which acts on a similar range of substrates. CYP3A4 increases to approximately 40% of adult levels in the fourth month of life and 72% at 12 months.[11][12]

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.

Recently CYP3A4 has also been identified in the brain, but its role in the central nervous system is still unknown.[13]

Mechanisms

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.[14][15]

Hydroxylation of an sp3 C-H bond is one of the ways in which CYP3A4 (and cytochrome P450 oxygenases) affects its ligand.[16] In fact, hydroxylation is sometimes followed by dehydrogenation, leading to more complex metabolites.[15] 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.[15]

Two mechanisms have been proposed as the primary pathway of hydroxylation in P450 enzymes.

Файл:Hydroxylation Mechanisms of Cytochrome P450 Enzymes.png
Two of the most commonly proposed mechanisms used for the hydroxylation of an sp3 C–H bond

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".[16]

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.[17][18][19][20][21] In some cases, this can lead to a fatal interaction with drugs like astemizole or terfenadine.[18] 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. The effects of grapefruit last from 3–7 days, with the greatest effects when juice is taken an hour previous to administration of the drug.[22]

In addition to grapefruit, other fruits have similar effects. Noni (Morinda citrifolia), for example, is a dietary supplement typically consumed as a juice and also inhibits CYP3A4.[23] Pomegranate juice has shown some inhibition in limited studies, but has not yet demonstrated the effect in humans.[24][25]

Variability

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 Шаблон:Lang. It can be supposed that this may be due to the induction of CYP3A4 on exposure to substrates.

CYP3A4 alleles that 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.[26] By contrast, CYP3A4*1G allele has more potent enzymatic activity compared to CYP3A4*1A (the wild-type allele).[27]

Variability in CYP3A4 function can be determined noninvasively by the erythromycin breath test (ERMBT). The ERMBT estimates Шаблон:Lang CYP3A4 activity by measuring the radiolabelled carbon dioxide exhaled after an intravenous dose of (14C-N-methyl)-erythromycin.[28]

Induction

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 aflatoxin 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.[29]

Induction of CYP3A4 has been shown to vary in humans depending on sex. Evidence shows an increased drug clearance by CYP3A4 in women, even when accounting for differences in body weight. A study by Wolbold 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.[30]

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 pregnenolone 16α-carbonitrile[31] 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.[31] This effect has been attributed to CYP3A4 regulation by the growth hormone signal transduction pathway.[31] In addition to providing an in vivo model, humanized CYP3A4 mice (hCYP3A4) have been used to further emphasize gender differences in CYP3A4 activity.[31]

CYP3A4 activity levels have also been linked to diet and environmental factors, such as duration of exposure to xenobiotic substances.[32] 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.[32] 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.

Turnover

Estimates of the turnover rate of human CYP3A4 vary widely. For hepatic CYP3A4, in vivo methods yield estimates of the enzyme half-life mainly in the range of 70 to 140 hours, whereas in vitro methods give estimates from 26 to 79 hours.[33] Turnover of gut CYP3A4 is likely to be a function of the rate of enterocyte renewal; an indirect approach based on the recovery of activity following exposure to grapefruit juice yields measurements in the 12- to 33-hour range.[33]

Technology

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.[34] A successful strategy in isolating the bound enzyme is the functional stabilization of monomeric CYP3A4 on silver nanoparticles produced from nanosphere lithography and analyzed via localized surface plasmon resonance spectroscopy (LSPR).[35] 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.[35]

Ligands

Following are the lists of selected substrates, inducers and inhibitors of CYP3A4. Where classes of agents are listed, there may be exceptions within the class.

Substrates

The substrates of CYP3A4 are the following substances:

Inhibitors

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.[36]
  • Moderate inhibitor being one that causes at least a 2-fold increase in the plasma AUC values, or 50–80% decrease in clearance.[36]
  • 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.[36]

The inhibitors of CYP3A4 are the following substances.

Strong inhibitors

Moderate inhibitors

Weak inhibitors

Inhibitors of unspecified potency

Inducers

Strong and moderate CYP3A4 inducers are drugs that decrease the AUC of sensitive substrates of a given pathway where CYP3A4 is involved by ≥80 percent and ≥50 to <80 percent, respectively.[76][112] Weak inducers decrease the AUC by ≥20 to <50 percent.[112]

The inducers of CYP3A4 are the following substances.

Strong inducers

Weak inducers

Inducers of unspecified potency

Interactive pathway map

Шаблон:IrinotecanPathway WP229

See also

References

Шаблон:Reflist

External links

Шаблон:NLM content Шаблон:PDB Gallery Шаблон:Cytochrome P450 Шаблон:Dioxygenases Шаблон:Enzymes Шаблон:Portal bar

  1. Шаблон:Cite journal
  2. Шаблон:Cite journal
  3. 3,0 3,1 3,2 3,3 Шаблон:NCBI RefSeq
  4. Шаблон:Cite journal
  5. Шаблон:EntrezGene
  6. Шаблон:Cite journal
  7. Шаблон:Cite journal
  8. Шаблон:Cite journal
  9. 9,0 9,1 Шаблон:Cite journal
  10. 10,0 10,1 Шаблон:Cite journal
  11. Шаблон:Cite journal
  12. Шаблон:Cite journal
  13. Шаблон:Cite journal
  14. Шаблон:Cite journal
  15. 15,0 15,1 15,2 Шаблон:Cite journal
  16. 16,0 16,1 Шаблон:Cite journal
  17. Шаблон:Cite journal
  18. 18,0 18,1 Шаблон:Cite journal
  19. Шаблон:Cite journal
  20. Шаблон:Cite journal
  21. Шаблон:Cite journal
  22. Шаблон:Cite journal
  23. Шаблон:Cite web
  24. Шаблон:Cite journal
  25. Шаблон:Cite journal
  26. Шаблон:Cite journal
  27. 27,0 27,1 Alkattan A, Alsalameen E. Polymorphisms of genes related to phase-I metabolic enzymes affecting the clinical efficacy and safety of clopidogrel treatment. Expert Opin Drug Metab Toxicol. 2021 Apr 30. doi: 10.1080/17425255.2021.1925249. Epub ahead of print. PMID 33931001.
  28. Шаблон:Cite journal
  29. Шаблон:Cite journal
  30. Шаблон:Cite journal
  31. 31,0 31,1 31,2 31,3 Шаблон:Cite journal
  32. 32,0 32,1 Шаблон:Cite journal
  33. 33,0 33,1 Шаблон:Cite journal
  34. Шаблон:Cite journal
  35. 35,0 35,1 Шаблон:Cite journal
  36. 36,000 36,001 36,002 36,003 36,004 36,005 36,006 36,007 36,008 36,009 36,010 36,011 36,012 36,013 36,014 36,015 36,016 36,017 36,018 36,019 36,020 36,021 36,022 36,023 36,024 36,025 36,026 36,027 36,028 36,029 36,030 36,031 36,032 36,033 36,034 36,035 36,036 36,037 36,038 36,039 36,040 36,041 36,042 36,043 36,044 36,045 36,046 36,047 36,048 36,049 36,050 36,051 36,052 36,053 36,054 36,055 36,056 36,057 36,058 36,059 36,060 36,061 36,062 36,063 36,064 36,065 36,066 36,067 36,068 36,069 36,070 36,071 36,072 36,073 36,074 36,075 36,076 36,077 36,078 36,079 36,080 36,081 36,082 36,083 36,084 36,085 36,086 36,087 36,088 36,089 36,090 36,091 36,092 36,093 36,094 36,095 36,096 36,097 36,098 36,099 36,100 36,101 36,102 36,103 36,104 36,105 36,106 36,107 36,108 36,109 36,110 36,111 36,112 36,113 36,114 36,115 36,116 36,117 Шаблон:Cite web Retrieved on 25 December 2008.
  37. 37,00 37,01 37,02 37,03 37,04 37,05 37,06 37,07 37,08 37,09 37,10 37,11 37,12 37,13 37,14 37,15 37,16 37,17 37,18 37,19 37,20 37,21 37,22 37,23 37,24 37,25 37,26 37,27 37,28 37,29 37,30 37,31 37,32 37,33 37,34 37,35 37,36 37,37 37,38 37,39 37,40 37,41 37,42 37,43 37,44 37,45 37,46 37,47 37,48 37,49 37,50 37,51 37,52 37,53 37,54 37,55 37,56 37,57 37,58 37,59 37,60 37,61 37,62 37,63 37,64 37,65 FASS (drug formulary): Swedish environmental classification of pharmaceuticals Facts for prescribers (Fakta för förskrivare). Retrieved July 2011
  38. 38,0 38,1 "Rinvoq: EPAR – Public assessment report" (PDF). European Medicines Agency. 5 March 2020. Archived (PDF) from the original on 21 July 2020. Retrieved 21 July 2020.
  39. 39,0 39,1 Austria-Codex (in German). Vienna: Österreichischer Apothekerverlag. 2020. Rinvoq 15 mg Retardtabletten.
  40. Шаблон:Cite web
  41. Шаблон:Cite web
  42. Шаблон:Cite book
  43. Шаблон:Cite journal
  44. Шаблон:Cite journal
  45. Шаблон:Cite journal
  46. Шаблон:Cite journal
  47. Шаблон:Cite web
  48. Шаблон:Cite journal
  49. Шаблон:Cite journal
  50. Шаблон:Cite journal
  51. Шаблон:Cite journal
  52. Шаблон:Cite journal
  53. Шаблон:Cite journal
  54. Шаблон:Cite web
  55. Шаблон:Cite journal
  56. Шаблон:Cite journal
  57. Шаблон:Cite journal
  58. Шаблон:Cite journal
  59. Шаблон:Cite journal
  60. Шаблон:Cite journal
  61. Шаблон:Cite journal
  62. 62,0 62,1 Шаблон:Cite journal
  63. Шаблон:Cite web
  64. Шаблон:Cite journal
  65. 65,0 65,1 Шаблон:Cite journal
  66. Шаблон:Cite journal
  67. Шаблон:Cite journal
  68. 68,0 68,1 68,2 68,3 68,4 Шаблон:Cite book
  69. Enzyme 1.14.13.32 at KEGG
  70. Шаблон:Cite web
  71. Шаблон:Cite journal
  72. Шаблон:Cite journal
  73. Шаблон:Cite journal
  74. Шаблон:Cite web
  75. 75,0 75,1 Шаблон:Cite journal
  76. 76,00 76,01 76,02 76,03 76,04 76,05 76,06 76,07 76,08 76,09 76,10 76,11 76,12 76,13 Шаблон:Cite journal
  77. 77,0 77,1 77,2 77,3 77,4 77,5 Шаблон:Cite bookШаблон:Page needed
  78. Шаблон:Cite journal
  79. Шаблон:Cite journal
  80. Шаблон:Cite journal
  81. 81,0 81,1 81,2 Шаблон:Cite journal
  82. 82,00 82,01 82,02 82,03 82,04 82,05 82,06 82,07 82,08 82,09 82,10 82,11 82,12 82,13 82,14 82,15 82,16 Шаблон:Cite web
  83. 83,0 83,1 Шаблон:Cite journal
  84. 84,0 84,1 Шаблон:Cite journal
  85. 85,0 85,1 Шаблон:Cite journal
  86. Шаблон:Cite journal
  87. Шаблон:Cite journal
  88. Шаблон:Cite journal
  89. Шаблон:Cite journal
  90. Шаблон:Cite journal
  91. Product Information: ORAVIG(R) buccal tablets, miconazole buccal tablets. Praelia Pharmaceuticals, Inc (per FDA), Cary, NC, 2013.
  92. Шаблон:Cite journal
  93. Шаблон:Cite web
  94. Шаблон:Cite journal
  95. Шаблон:Cite journal
  96. Шаблон:Cite journal
  97. Шаблон:Cite journal
  98. Шаблон:Cite journal
  99. Шаблон:Cite web
  100. Шаблон:Cite journal
  101. Шаблон:Cite journal
  102. Шаблон:Cite journal
  103. 103,0 103,1 Non-nucleoside reverse-transcriptase inhibitors have been shown to both induce and inhibit CYP3A4.
  104. Шаблон:Cite journal
  105. Шаблон:Cite web
  106. Шаблон:Cite journal
  107. Шаблон:Cite journal
  108. Шаблон:Cite journal
  109. Шаблон:Cite journal
  110. Шаблон:Cite journal
  111. Шаблон:Cite journal
  112. 112,0 112,1 Шаблон:Cite journal
  113. Шаблон:Cite web
  114. Шаблон:Cite journal
  115. Шаблон:Cite journal
  116. Шаблон:Cite journal