BIOSYNTHESIS OF DOLICHOL AND CHOLESTEROL IN RAT-LIVER PEROXISOMES

Isolated rat liver peroxisomes contain the complete enzymatic machinery required for the synthesis of both cholesterol and dolichol from farnesyl pyrophosphate. Additionally, the whole or part of the initial portion of the mevalonate pathway between acetyl-CoA and farnesyl pyrophosphate is also present in peroxisomes. Cholesterol and dolichol biosynthesis in peroxisomes is more complete than in ER since peroxisomes contain high concentrations of sterol carrier protein-2, a protein that stimulates both dolichol and cholesterol biosynthesis. Approximately 50 and 20% of the total hepatic dolichol and cholesterol biosynthesis is associated with rat liver peroxisomes, respectively. Upon dietary and drug treatments the synthesis of these lipids displays different regulation in peroxisomes and ER.