Could catalyze the introduction of a 9alpha-hydroxyl moiety into the ring B of 3-ketosteroid substrates. Binds 1 [2Fe-2S] cluster per subunit. Binds 1 Fe cation. Homotrimer. The two-component system 3-ketosteroid-9-alpha-monooxygenase is composed of an oxygenase component KshA and a reductase component KshB. By cholic acid.