Last modified: Fri Jul 9 14:32:38 BST 2004

Steroid carbon nomenclature

Trivial name: Androstenedione
Systematic name: Androst-4-ene-3,17-dione
Molecular formula: C19H26O2
CAS Number: 63-05-8
Merck Index (11th Ed) Number: 671


Pathway: Androstenedione -> 6ß-Hydroxyadrostenedione
Reaction: steroid ß-hydroxylation at C6
Enzyme: steroid 6ß-hydroxylase, CYP3A [1]
EC Enzyme: P450HP, CYP4B1 [2]

Substrate [3]

Pathway: Androstenedione -> 11ß-Hydroxyandrostenedione
Reaction: steroid ß-hydroxylation at C11
Enzyme: P450c11 (steroid 11ß-hydroxylase), CYP11B

Substrate [4]

Pathway: Androstenedione -> 15alpha-Hydroxyandrostenedione
Reaction: steroid alpha-hydroxylation at C15
Enzyme: P45015alpha (steroid 15alpha-hydroxylase), CYP2B

Substrate [4]

Pathway: Androstenedione -> 16alpha-Hydroxyandrostenedione
Reaction: steroid alpha-hydroxylation at C16
Enzyme: P45016alpha (steroid 16alpha-hydroxylase), CYP2B

Substrate [4]

Pathway: Androstenedione -> 16ß-Hydroxyandrostenedione
Reaction: steroid ß-hydroxylation at C16
Enzyme: P45016ß (steroid 16ß-hydroxylase), CYP2B

Substrate [3]

Pathway: Androstenedione -> 19-Hydroxyandrostenedione
Reaction: steroid hydroxylation at C19
Enzyme: P450c19 (steroid 19-hydroxylase), CYP11B

Substrate [1]

Pathway: Androstenedione -> Estrone + HCOOH
Reaction: aromatase (aromatisation of the A ring and C19 demethylation)
Enzyme: P450arom (aromatase), CYP19

Product [1]

Pathway: 17alpha-Hydroxyprogesterone -> Androstenedione + Acetate
Reaction: cleavage of steroid C17-C20 bond
Enzyme: P450c17 (steroid 17alpha-hydroxylase/17,20-lyase), CYP17


  1. Chang, T.K., Teixeira, J., Gil, G. and Waxman, D.J. (1993) The lithocholic acid 6ß-hydroxylase cytochrome P-450, CYP 3A10, is an active catalyst of steroid-hormone 6ß-hydroxylation. Biochem. J. 291, 429-433.
  2. Waxman, D.J., Lapenson, D.P., Aoyama, T., Gelboin, H.V., Gonzalez, F.J. and Korzekwa, K. (1991) Steroid hormone hydroxylase specificities of eleven cDNA-expressed human cytochrome P450s. Arch. Biochem. Biophys. 290, 160-166.
  3. Ruckpaul, K. and Rein, H., Eds. (1990) Frontiers in Biotransformation, vol. 3: Molecular Mechanisms of Adrenal Steroidogenesis and Aspects of Regulation and Application. Taylor & Francis, London.
  4. Szklarz, G.D., He, Y.Q., Kedzie, K.M., Halpert, J.R. and Burnett, V.L. (1996) Elucidation of amino acid residues critical for unique activities of rabbit cytochrome P450 2B5 using hybrid enzymes and reciprocal site-directed mutagenesis with rabbit cytochrome P450 2B4. Arch. Biochem. Biophys. 327, 308-318.

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