The effect of fasting on the activity of liver carnitine palmitoyltransferase and its inhibition by malonyl-CoA.

The effect of fasting on palmitoyl-CoA: carnitine palmitoyltransferase (EC 2.3.1.21) in rat liver mitochondria and its inhibition by malonyl-CoA has been investigated. The activity of the outer carnitine palmitoyltransferase (transferase I) is nearly doubled after 24 h fasting, while the activity of total carnitine palmitoyltransferase (transferase I + II) increases only about 25%. The inhibition of the increased outer transferase by malonyl-CoA is decreased in fasting rats. The results suggest that carnitine palmitoyltransferase less sensitive to malonyl-CoA is exposed on the outer surface of the inner mitochondrial membrane in fasting, thus reducing the latency of the enzyme.