{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n The CYP3A gene cluster encodes several enzymes with overlapping yet distinct roles in the metabolism of endogenous hormones and xenobiotics. In particular, CYP3A7 is best known as the predominant cytochrome P450 in the fetal liver, where it catalyzes the 16α‐hydroxylation of steroid hormones such as dehydroepiandrosterone sulfate and estrone and participates in retinoic acid clearance (see."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": " Although CYP3A7 is normally silenced after birth, a variant allele (CYP3A7*1C) confers persistent postnatal expression in a subset of individuals. This allele achieves its effect by replacing part of the CYP3A7 promoter with corresponding regulatory sequences from CYP3A4, thereby enhancing binding of nuclear receptors and transcription factors that support robust expression in liver and extrahepatic tissues such as the intestine and endometrium."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}, {"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In adults expressing CYP3A7, the enzyme may contribute a considerable fraction of total CYP3A content—up to 9–36% in some livers—and is implicated in modulating circulating steroid levels as well as influencing the metabolism of drugs. Although its intrinsic catalytic efficiency toward xenobiotic substrates is generally lower than that of CYP3A4, CYP3A7 appears to play a complementary role when the activities of other CYP3A members (for example, CYP3A4 and CYP3A5) are variable."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": " Moreover, coordinated regulation by hepatic transcription factors—including C/EBPα and HNF‐3 family members—suggests that CYP3A7 expression and its contribution to overall metabolic capacity is governed by complex developmental and tissue‐specific signals."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": " \n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n The CYP3A7–CYP3A51P region is part of this intricate gene cluster. While CYP3A7 encodes a functional enzyme with significant roles in fetal steroid metabolism and, in selected adults, drug processing, CYP3A51P is regarded as a pseudogene that contributes structurally to the locus without producing a catalytically active protein."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In summary, the functional importance of CYP3A7 lies in its developmental role in hormone metabolism and—in individuals carrying the CYP3A7*1C allele—in its persistent adult expression that can influence both endogenous steroid homeostasis and drug clearance. Understanding the regulation and variable expression of CYP3A7 is therefore critical for elucidating interindividual differences in both hormonal balance and pharmacokinetic responses.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Oliver Burk, Heike Tegude, Ina Koch, et al. 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