The Stoichiometry of the Conversion of Cholesterol and Hydroxycholesterols to Pregnenolone (3β-Hydroxypregn-5-en-20-one) Catalysed by Adrenal Cytochrome P -450 | Zendy

Mikio Shikita | Zendy; Peter F. Hall | Zendy

Open Access

The Stoichiometry of the Conversion of Cholesterol and Hydroxycholesterols to Pregnenolone (3β-Hydroxypregn-5-en-20-one) Catalysed by Adrenal Cytochrome P -450

Author(s) -

Mikio Shikita,

Peter F. Hall

Publication year - 1974

Publication title -

proceedings of the national academy of sciences

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 5.011

H-Index - 771

eISSN - 1091-6490

pISSN - 0027-8424

DOI - 10.1073/pnas.71.4.1441

Subject(s) - pregnenolone , chemistry , cleavage (geology) , cytochrome , cholesterol side chain cleavage enzyme , stoichiometry , cholesterol , stereochemistry , biochemistry , organic chemistry , steroid , cytochrome p450 , metabolism , enzyme , biology , hormone , paleontology , fracture (geology)

The stoichiometry of the side-chain cleavage of cholesterol (cholest-5-en-3β-ol), 20α-hydroxycholesterol (cholest-5-ene-3β,20α-diol), and 20α,22-dihydroxycholesterol (cholest-5-ene-3β,20α,22-triol) has been examined with respect to TPNH, oxygen and H+ . Side-chain cleavage of cholesterol can be described by the following equation:Cholesterol + 3TPNH + 3H+ + 3O2 → Pregnenolone (3β-hydroxypregn-5-ene-20-one) + isocapraldehyde + 3 TPN+ 4H2 OStoichiometry of 20 α-hydroxycholesterol is 2TPNH and 2O2 per mole of cleavage and with 20α, 22-dihydroxycholesterol the values are 1:1:1. In addition 1 mole of H+ is consumed per mole of TPNH oxidized in each of these reactions. These observations are in keeping with a mechanism previously proposed in the literature, namely:Cholesterol → 20α-OH-Cholesterol → 20α, 22-di-OH-Cholesterol → pregnenolone Discordant observations are reviewed and it is concluded that insufficient data are available to sustain objections to this pathway.

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