CYP3A4

Source: NCBI Gene, accessed 2026-10-07.

Protein

Cytochrome P450 3A4

Function (excerpt)

A cytochrome P450 monooxygenase involved in the metabolism of sterols, steroid hormones, retinoids and fatty acids. Mechanistically, uses molecular oxygen inserting one oxygen atom into a substrate, and reducing the second into a water molecule, with two electrons provided by NADPH via cytochrome P450 reductase (NADPH--hemoprotein reductase). Catalyzes the hydroxylation of carbon-hydrogen bonds. Exhibits high catalytic activity for the formation of hydroxyestrogens from estrone (E1) and 17beta-estradiol (E2), namely 2-hydroxy E1 and E2, as well as D-ring hydroxylated E1 and E2 at the C-16 position. Plays a role in the metabolism of androgens, particularly in oxidative deactivation of testosterone. Metabolizes testosterone to less biologically active 2beta- and 6beta-hydroxytestosterones.

Pathway

Steroid hormone biosynthesis. Cofactor metabolism; retinol metabolism. Steroid metabolism; cholesterol metabolism. Lipid metabolism; fatty acid metabolism.

Subcellular location

Endoplasmic reticulum membrane; Microsome membrane.

Tissue specificity

Expressed in prostate and liver. According to some authors, it is not expressed in brain. According to others, weak levels of expression are measured in some brain locations. Also expressed in epithelium of the small intestine and large intestine, bile duct, nasal mucosa, kidney, adrenal cortex, epithelium of the gastric mucosa with intestinal metaplasia, gallbladder, intercalated ducts of the pancreas, chief cells of the parathyroid and the corpus luteum of the ovary (at protein level).

Associated conditions

Vitamin D-dependent rickets 3 (VDDR3).

Source: UniProtKB/Swiss-Prot P08684, release 2026_03, licensed CC BY 4.0. This is the protein’s normal biology, not evidence about post-drug syndromes; associated conditions are inherited disorders of the gene, not PFS, PSSD or PRSD.

Written for the whole drug metabolism family, not for CYP3A4 specifically.