Editing CYP3A4 (section)

{{Short description|Enzyme that metabolizes substances by oxidation}}
{{Use dmy dates|date=December 2023}}
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{{Use American English|date=February 2024}}
{{Infobox enzyme
| name = CYP3A4
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| EC_number = 1.14.14.56
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'''Cytochrome P450 3A4''' (abbreviated '''CYP3A4''') ({{EC number|1.14.13.97}}) 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 [[organic redox reaction|oxidizes]] small foreign organic molecules ([[xenobiotic]]s), such as [[toxin]]s 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 [[furanocoumarin]]s 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]].<ref name="pmid8269949">{{cite journal | vauthors = Hashimoto H, Toide K, Kitamura R, Fujita M, Tagawa S, Itoh S, Kamataki T | title = Gene structure of CYP3A4, an adult-specific form of cytochrome P450 in human livers, and its transcriptional control | journal = European Journal of Biochemistry | volume = 218 | issue = 2 | pages = 585–95 | date = December 1993 | pmid = 8269949 | doi = 10.1111/j.1432-1033.1993.tb18412.x | doi-access = free }}</ref> This gene is part of a cluster of cytochrome P450 genes on [[chromosome 7 (human)|chromosome 7q22.1]].<ref name="pmid1391968">{{cite journal | vauthors = Inoue K, Inazawa J, Nakagawa H, Shimada T, Yamazaki H, Guengerich FP, Abe T | title = Assignment of the human cytochrome P-450 nifedipine oxidase gene (CYP3A4) to chromosome 7 at band q22.1 by fluorescence in situ hybridization | journal = The Japanese Journal of Human Genetics | volume = 37 | issue = 2 | pages = 133–8 | date = June 1992 | pmid = 1391968 | doi = 10.1007/BF01899734 | doi-access = free }}</ref> 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.<ref name="refseq"/>