Secondary regulatory sites in rat liver cholesterol biosynthesis: role of 5-pyrophosphomevalonate decarboxylase.

The activity of 5-pyrophosphomevalonate decarboxylase in 43,000 g supernatant fractions from livers and kidneys of male adult rats has been determined. Enzyme activity in liver is significantly increased when rats are fed a diet containing 3% cholestyramine (268% of control rats) and decreased when fed a diet containing 2% cholesterol (25% of control rats). No circadian rhythm of enzyme activity is found in liver or kidneys. These results show that variations in hepatic cholesterogenesis affect the activity of 5-pyrophosphomevalonate decarboxylase in a similar way as other enzymes involved in the biosynthesis of cholesterol.