The conversion of cholest-7-en-3β-ol into cholesterol. General comments on the mechanism of the introduction of double bonds in enzymic reactions
- 30 November 1967
- journal article
- research article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 105 (3), 1187-1194
- https://doi.org/10.1042/bj1051187
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.This publication has 9 references indexed in Scilit:
- The stereochemistry of the hydrogen elimination in the biological conversion of cholest-7-en-3-β-ol into cholesterolBiochemical Journal, 1967
- Metabolic Transformations of CholestenediolsJournal of Biological Chemistry, 1965
- PATHWAYS OF ENZYMIC SYNTHESIS AND CONVERSION TO CHOLESTEROL OF DELTA5,7,24-CHOLESTATRIEN-3BETAO1 AND OTHER NATURALLY OCCURRING STEROLS1965
- Stereochemistry of the exchange catalyzed by succinic dehydrogenaseBiochemical and Biophysical Research Communications, 1964
- Concerning the Stereochemistry and Mechanism of the Bacterial C-1,2 Dehydrogenation of SteroidsJournal of Biological Chemistry, 1963
- Mechanism of the Succinic Dehydrogenase Catalysed ReactionNature, 1963
- CONVERSION OF 5ALPHA-CHOLESTAN-3BETA-OL TO DELTA7-5ALPHA-CHOLESTEN-3BETA-OL IN COCKROACHES1963
- Stereochemistry of the Succinic Dehydrogenase SystemNature, 1961
- ON THE MECHANISM OF AN ANAEROBIC EXCHANGE REACTION CATALYZED BY SUCCINIC DEHYDROGENASE PREPARATIONSJournal of Biological Chemistry, 1956