PMVK is a peroxisomal enzyme that catalyzes the conversion of mevalonate 5-phosphate into mevalonate 5-diphosphate, the fifth reaction of the cholesterol biosynthetic pathway. Studies in rat show that the message level and the enzyme activity of PMVK is regulated by sterol, and that this regulation is coordinated with 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme of cholesterol biosynthesis.