Probably involved in the degradation of cholesterol (PubMed:21642460). In vitro, catalyzes the introduction of a 9alpha-hydroxyl moiety into the ring B of 3-ketosteroid substrates such as 1,4-androstadiene-3,17-dione (ADD), 4-androstene-3,17-dione (AD), 4-androstene-17beta-ol-3-one (testosterone), 4-pregnene-3,20-dione (progesterone), 19-nor-4-androstene-3,17-dione, 1-(5alpha)-androstene-3,17-dione, 5alpha-androstane-3,17-dione, 5beta-androstane-3,17-dione, 5alpha-androstane-17beta-ol-3-one (stanolon), 11beta-hydrocortisone, 3-oxo-23,24-bisnorcholesta-4-en-22-oate (4-BNC), 23,24-bisnorcholesta-4-ene-22-oate, 3-oxo-23,24-bisnorcholesta-1,4-dien-22-oate (1,4-BNC) and 3-oxo-23,24-bisnorcholesta-1,4-dien-22-oyl-coenzyme A thioester (1,4-BNC-CoA) (PubMed:21642460, PubMed:25049233). KshA5 has the broadest substrate range without a clear substrate preference and is active with Delta-4, Delta-1,4, 5alpha-H and 5beta-H steroids, as well as with steroids having bulky aliphatic side chains and an isopropionyl side chain at C17. androsta-1,4-diene-3,17-dione + 2 H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = 9alpha-hydroxyandrosta-1,4-diene-3,17-dione + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] Binds 1 [2Fe-2S] cluster per subunit. Binds 1 Fe cation. kcat is 1.7 sec(-1) for 1,4-BNC-CoA as substrate (at pH 7.0 and 22 degrees Celsius). kcat is 0.8 sec(-1) for 5alpha-androstan-3,17-dione, AD and testosterone as substrates (at pH 7.0 and 22 degrees Celsius). kcat is 0.7 sec(-1) for ADD as substrate (at pH 7.0 and 22 degrees Celsius). kcat is 0.6 sec(-1) for 4-BNC as substrate (at pH 7.0 and 22 degrees Celsius). kcat is 0.5 sec(-1) for 1,4-BNC as substrate (at pH 7.0 and 22 degrees Celsius). Steroid metabolism; cholesterol degradation. Homotrimer. The two-component system 3-ketosteroid-9-alpha-monooxygenase is composed of an oxygenase component KshA and a reductase component KshB. By cholesterol, progesterone, AD and cholic acid.