Preincubation of a 10,000 x g supernatant from rat liver for 20 min at 37° increased the subsequent incorporation of [14C]acetate into cholesterol by 8 to 20 fold. Cholesterol synthesis from [14C]citrate was comparably activated. Optimal activation occurred at 0.6 to 1.2 mM magnesium; no activation was observed at 6.0 mM Mg2+. The activated rate of cholesterol synthesis from acetate (10 to 25 nmoles per g wet weight per hour) was higher than that previously reported for rat liver homogenates. Optimal activation of cholesterol biosynthesis from [14C]acetate was also obtained when isolated microsomes and cytosol were preincubated and assayed together. Much lower activation was seen when these fractions were preincubated separately and recombined for assay. Activation of cholesterol biosynthesis was not seen with [14C]mevalonate as substrate. Conversion of [14C]acetate to both fatty acids and CO2 was tripled by preincubation, while conversion to acetoacetate was unaffected. The data suggest that this activation is specific for those enzymes of cholesterol biosynthesis which convert acetyl CoA to mevalonate and may reflect the reversal in vitro of a physiological control on cholesterol biosynthesis.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|State||Published - Dec 1 1973|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology