EC - Ketosteroid monooxygenase

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IntEnz Enzyme Nomenclature


Accepted name:
ketosteroid monooxygenase
Other names:
17α-hydroxyprogesterone, NADPH2:oxygen oxidoreductase (20-hydroxylating, side-chain cleaving)
androstenedione, NADPH2:oxygen oxidoreductase (17-hydroxylating, lactonizing)
progesterone, NADPH2:oxygen oxidoreductase (20-hydroxylating, ester-producing)
steroid-ketone monooxygenase
Systematic name:
ketosteroid,NADPH:oxygen oxidoreductase (20-hydroxylating, ester-producing/20-hydroxylating, side-chain cleaving/17-hydroxylating, lactonizing)




A single FAD-containing enzyme catalyses three types of monooxygenase (Baeyer-Villiger oxidation) reaction. The oxidative esterification of a number of derivatives of progesterone to produce the corresponding 17α-hydroxysteroid 17-acetate ester, such as testosterone acetate, is shown in Reaction (2). The oxidative lactonization of a number of derivatives of androstenedione to produce the 13,17-secoandrosteno-17,13α-lactone, such as testololactone, is shown in Reaction (3). The oxidative cleavage of the 17β-side-chain of 17α-hydroxyprogesterone to produce androstenedione and acetate is shown in Reaction (4). Reaction (2) is also catalysed by EC (progesterone monooxygenase), and Reactions (3) and (4) correspond to that catalysed by EC (androst-4-ene-3,17-dione monooxygenase). The possibility that a single enzyme is responsible for the reactions ascribed to EC and EC in other tissues cannot be excluded.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0047086
CAS Registry Number: 9044-53-5


  1. Katagiri, M. and Itagaki, E.
    A steroid ketone monooxygenase from Cylindrocarpon radicicola.
    In: Müller, F. (Ed.) Chemistry and Biochemistry of Flavoenzymes, CRC Press, Florida, 1991, 102-108
  2. Itagaki, E.
    Studies on a steroid monooxygenase from Cylindrocarpon radicicola ATCC 11011. Purification and characterization.
    J. Biochem. (Tokyo) 99: 815-824 (1986). [PMID: 3486863]
  3. Itagaki, E.
    Studies on a steroid monooxygenase from Cylindrocarpon radicicola ATCC11011. Oxygenative lactonization of androstenedione to testololactone.
    J. Biochem. (Tokyo) 99: 825-832 (1986). [PMID: 3486864]

[EC created 1999]