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. 1967 Dec;105(3):1187–1194. doi: 10.1042/bj1051187

The conversion of cholest-7-en-3β-ol into cholesterol. General comments on the mechanism of the introduction of double bonds in enzymic reactions

S Marsh Dewhurst 1, M Akhtar 1
PMCID: PMC1198440  PMID: 16742545

Abstract

Convenient syntheses of 6β-tritiated Δ7-cholestenol and 3α-tritiated Δ7-cholestene-3β,5α-diol are described. It was shown that the conversion of 6β-tritiated Δ7-cholestenol into cholesterol is accompanied by the complete retention of label. It was unambiguously established that the overall reaction leading to the introduction of the double bond in the 5,6-position in cholesterol occurs via a cis-elimination involving the 5α- and 6α-hydrogen atoms and that during this process the 6β-hydrogen atom remains completely undisturbed. Metabolic studies with 3α-tritiated Δ7-cholestene-3β,5α-diol revealed that under anaerobic conditions the compound is not converted into cholesterol. This observation, coupled with the previous work of Slaytor & Bloch (1965), is interpreted to exclude a hydroxylation–dehydration mechanism for the origin of the 5,6-double bond in cholesterol. It was also shown that under aerobic conditions 3α-tritiated Δ7-cholestene-3β,5α-diol is efficiently converted into cholesterol and that this conversion occurs through the intermediacy of 7-dehydrocholesterol. Cumulative experimental evidence presented in this paper and elsewhere is used to suggest that the 5,6-double bond in cholesterol originates through an oxygen-dependent dehydrogenation process and a hypothetical mechanism for this and related reactions is outlined.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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