3 Hydroxy 9,10 secoandrosta 1,3,5(10) triene 9,17 dione monooxygenase

3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione monooxygenase (EC 1.14.14.12, HsaA) is an enzyme with systematic name 3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione,FMNH2:oxygen oxidoreductase. This enzyme catalyses the following chemical reaction

3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione + FMNH₂ + O₂ ⇌ 3,4-dihydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione + FMN + H₂O

This bacterial enzyme participates in the degradation of several steroids, including cholesterol and testosterone.