Steroid 17alpha-monooxygenase

{{infobox enzyme

| Name = steroid 17-alpha-monooxygenase

| EC_number = 1.14.99.9

| CAS_number = 9029-67-8

| GO_code = 0004508

| image =

| width =

| caption =

}}

In enzymology, a steroid 17alpha-monooxygenase ({{EC number|1.14.99.9}}) is an enzyme that catalyzes the chemical reaction

:a steroid + AH₂ + O₂ $\backslash rightleftharpoons$ a 17alpha-hydroxysteroid + A + H₂O

The 3 substrates of this enzyme are steroid, an electron acceptor AH₂, and O₂, whereas its 3 products are 17alpha-hydroxysteroid, the reduction product A, and H₂O.{{cite journal | vauthors = Lynn WS, Brown RH | title = The conversion of progesterone to androgens by testes | journal = The Journal of Biological Chemistry | volume = 232 | issue = 2 | pages = 1015–30 | date = June 1958 | pmid = 13549484 }}{{cite journal | vauthors = Yoshida KI, Oshima H, Troen P | title = Studies of the human testis. XIII. Properties of nicotinamide adenine dinucleotide (reduced form)-linked 17 alpha-hydroxylation | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 50 | issue = 5 | pages = 895–9 | date = May 1980 | pmid = 6966286 | doi = 10.1210/jcem-50-5-895 }}

This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derive from O miscellaneous. The systematic name of this enzyme class is steroid,hydrogen-donor:oxygen oxidoreductase (17alpha-hydroxylating). Other names in common use include steroid 17alpha-hydroxylase, cytochrome P-45017alpha, cytochrome P-450 (P-45017alpha,lyase), and 17alpha-hydroxylase-C17,20 lyase. This enzyme participates in c21-steroid hormone metabolism. It has 3 cofactors: NADH, NADPH, and Heme.