3RUK, 3SWZ, 4NKV, 4NKW, 4NKX, 4NKY, 4NKZ
Cytochrome P450 17A1, also called steroid 17α-monooxygenase, 17α-hydroxylase, 17,20 lyase, or 17,20 desmolase, is an enzyme of the hydroxylase type that in humans is encoded by the CYP17A1 gene on chromosome 10. It is ubiquitously expressed in many tissues and cell types, including the zona reticularis of the adrenal cortex and zona fasciculata as well as gonadal tissues. This gene encodes a member of the superfamily of enzymes. The cytochrome P450 proteins are generally regarded as monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids, and other lipids, including the remarkable carbon-carbon bond scission catalyzed by this enzyme. This protein localizes to the endoplasmic reticulum. It has both 17α-hydroxylase and 17,20-lyase activities, and is a key enzyme in the steroidogenic pathway that produces progestins, mineralocorticoids, glucocorticoids, androgens, and estrogens. More specifically, CYP17A1 acts upon pregnenolone and progesterone to add a hydroxyl (-OH) group at carbon 17 of the steroid D ring (the hydroxylase activity), or acts upon 17α-hydroxyprogesterone and 17α-hydroxypregnenolone to split the side-chain off the steroid nucleus (the lyase activity). The CYP17A1 gene also contains one of 27 SNPs associated with increased risk of coronary artery disease.