Enzyme studies on the esterification of vitamin D in rat tissues
- 1 September 1968
- journal article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 109 (3), 457-467
- https://doi.org/10.1042/bj1090457
Abstract
1. The mechanism of vitamin D esterification in the rat was studied with liver, small-intestinal mucosa, pancreatic juice and blood plasma as enzyme sources and [1−3H]cholecalciferol, [U−14C]ergocalciferol and [4−14C]cholesterol as substrates. 2. No esterification of vitamin D could be detected with liver preparations nor with homogenates or acetone-dried powder extracts of intestinal mucosa. 3. Pancreatic juice esterified [1−3H]cholecalciferol with oleic acid, and specificity studies indicated that a cholesterol-esterifying enzyme was using vitamin D as substrate. 4. Plasma cholesterol-esterifying enzyme also esterified vitamin D. 5. The specificity of the esterification reaction is discussed in relation to (a) the molecular structure of the substrates and (b) their availability, in a micellar solution, to the enzyme. 6. It is concluded that cholesterol-esterifying enzymes esterify vitamin D in vivo during absorption from the small intestine and while it is transported in blood.Keywords
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