該基因編碼細胞色素p450酶超家族的一個成員。細胞色素p450蛋白是一種單加氧酶，催化藥物代謝和膽固醇、類固醇和其他脂質的合成。該蛋白定位于內質網，由糖皮質激素和一些藥物誘導表達。這種酶參與了目前使用的大約一半藥物的代謝，包括對乙酰氨基酚、可待因、環孢素A、地西泮和紅霉素。這種酶也能代謝一些類固醇和致癌物。該基因是7q21.1染色體上一組細胞色素p450基因的一部分。以前人們認為另一個cyp3a基因cyp3a3存在；然而，現在人們認為這個序列代表cyp3a4的轉錄變體。另外，還發現了編碼不同亞型的剪接轉錄變體。[由RefSeq提供，2011年2月]
This gene encodes 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. This 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 in use today, including acetaminophen, codeine, cyclosporin A, diazepam and erythromycin. The enzyme also metabolizes some steroids and carcinogens. This gene is part of a cluster of cytochrome P450 genes on chromosome 7q21.1. 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. [provided by RefSeq, Feb 2011]