It is shown that the 7-dehydrocholesterol reductase-catalysed conversion of 7-dehydrocholesterol into cholesterol (II), with a 105000g microsomal pellet of rat liver in the presence of [4−3H2]NADPH, results in the transfer of radioactivity to the 7α-position of cholesterol. When the conversion is carried out in the presence of tritiated water the label is introduced exclusively at the 8β-position. However, when the conversion of 7-dehydrocholesterol into cholesterol is performed with a 500g supernatant of rat liver homogenate the radioactivity is incorporated at both the 7α- and the 8β-position. Evidence is provided for the presence of an enzyme system in the 500g supernatant that catalyses an equilibration of hydrogen atoms between those at the 4-position of NADPH and those of water. The work with stereospecifically labelled cofactors shows that both the equilibrating system and the 7-dehydrocholesterol reductase utilize the 4B-hydrogen atom of NADPH. In the light of these results a mechanism for the reduction of carbon–carbon double bonds is discussed.
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February 1968
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Research Article|
February 01 1968
The biological conversion of 7-dehydrocholesterol into cholesterol and comments on the reduction of double bonds
D. C. Wilton;
D. C. Wilton
1Department of Physiology and Biochemistry, University of Southampton
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K A Munday;
K A Munday
1Department of Physiology and Biochemistry, University of Southampton
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S. J. M. Skinner;
S. J. M. Skinner
1Department of Physiology and Biochemistry, University of Southampton
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M Akhtar
M Akhtar
1Department of Physiology and Biochemistry, University of Southampton
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Publisher: Portland Press Ltd
© 1968 The Biochemical Society
1968
Biochem J (1968) 106 (4): 803–810.
Citation
D. C. Wilton, K A Munday, S. J. M. Skinner, M Akhtar; The biological conversion of 7-dehydrocholesterol into cholesterol and comments on the reduction of double bonds. Biochem J 1 February 1968; 106 (4): 803–810. doi: https://doi.org/10.1042/bj1060803
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