Last modified: Tue Jul 6 10:51:09 BST 2004

Steroid carbon nomenclature

Trivial names: Cholesterol; Cholesterin
Systematic name: Cholest-5-en-3ß-ol
Molecular formula: C27H46O
CAS Number: 57-88-5
Merck Index (11th Ed) Number: 2204

Substrate [1]

Pathway: Cholesterol -> Pregnenolone + Isocaproaldehyde
Reaction: cholesterol side-chain cleavage (hydroxylation at C22 and C20 and cleavage of C20-C22 bond)
Enzyme: P450scc (cholesterol side-chain cleavage), CYP11A1

Substrate [2]

Pathway: Cholesterol -> 7alpha-Hydroxycholesterol
Reaction: steroid alpha-hydroxylation at C7
Enzyme: P4507alpha (cholesterol 7alpha-monooxygenase), CYP7A


  1. 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.
  2. Jelinek, D.F., Andersson, S., Slaughter, C.A. and Russell, D.W. (1990) Cloning and regulation of cholesterol 7alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis. J. Biol. Chem. 265, 12012-12019.

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