Last modified: Tue Jul 6 11:37:03 BST 2004

Steroid carbon nomenclature

Trivial name: Testosterone
Systematic name: 17ß-Hydroxyandrost-4-en-3-one
Molecular formula: C19H28O2
CAS Number: 58-22-0
Merck Index (11th Ed) Number: 9109

Substrate [1]

Pathway: Testosterone -> 2ß-Hydroxytestosterone
Reaction: steroid 2ß-hydroxylation at C2
Enzyme: steroid 2ß-hydroxylase, CYP3A


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

Substrate [3]

Pathway: Testosterone -> 7alpha-Hydroxytestosterone
Reaction: steroid alpha-hydroxylation at C7
Enzyme: testosterone 7alpha-hydroxylase, CYP2A1

Substrate [4]

Pathway: Testosterone -> 11alpha-Hydroxytestosterone
Reaction: steroid alpha-hydroxylation at C11
Enzyme: P450NMb, CYP2G1

Substrate [5]

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


Pathway: Testosterone -> 15alpha-Hydroxytestosterone
Reaction: steroid alpha-hydroxylation at C15
Enzyme: P45015alpha (testosterone 15alpha-hydroxylase), CYP2A [6]
EC Enzyme: P450NMb, CYP2G1 [4]


Pathway: Testosterone -> 16alpha-Hydroxytestosterone
Reaction: steroid alpha-hydroxylation at C16
Enzyme: P45016alpha (testosterone 16alpha-hydroxylase), CYP2B [7]
EC Enzyme: P45016alpha (testosterone 16alpha-hydroxylase), CYP2D [8]
EC Enzyme: P450NMb, CYP2G1 [4]

Substrate [4]

Pathway: Testosterone -> 16ß-Hydroxytestosterone
Reaction: steroid ß-hydroxylation at C16
Enzyme: P450NMb, CYP2G1


  1. 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.
  2. 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.
  3. Nagata, K., Matsunaga, T., Gillette, J., Gelboin, H.V. and Gonzalez, F.J. (1987) Rat testosterone 7alpha-hydroxylase. Isolation, sequence, and expression of cDNA and its developmental regulation and induction by 3-methylcholanthrene. J. Biol. Chem. 262, 2787-2793.
  4. Ding, X. and Coon, M.J. (1994) Steroid metabolism by rabbit olfactory-specific P450 2G1. Arch. Biochem. Biophys. 315, 454-459.
  5. 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.
  6. Matsunaga, T., Nagata, K., Holsztynska, E.J., Lapenson, D.P., Smith, A., Kato, R., Gelboin, H.V., Waxman, D.J. and Gonzalez, F.J. (1988) Gene conversion and differential regulation in the rat P-450 IIA gene subfamily. Purification, catalytic activity, cDNA and deduced amino acid sequence, and regulation of an adult male-specific hepatic testosterone 15alpha-hydroxylase. J. Biol. Chem. 263, 17995-18002.
  7. Noshiro, M. Lakso, M., Kawajiri, K. and Negishi, M. (1988) Rip locus: regulation of female-specific isozyme (I-P-45016alpha) of testosterone 16alpha-hydroxylase in mouse liver, chromosome localization, and cloning of P-450 cDNA. Biochemistry 27, 6434-6443.
  8. Wong, G., Itakura, T., Kawajiri, K., Skow, L. and Negishi, M. (1989) Gene family of male-specific testosterone 16alpha-hydroxylase (C-P-45016alpha) in mice. Organization, differential regulation, and chromosome localization. J. Biol. Chem. 264, 2920-2927.

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