Carnitine palmitoyltransferase. Activation by palmitoyl-CoA and inactivation by malonyl-CoA

Extraction of rat liver mitochondria twice with 0.5% Triton X-100 in a salt-free medium leaves less than 10% of the carnitine palmitoyltransferase membrane bound. The remaining membrane-bound enzyme is inhibited virtually completely by 10 microM malonyl-CoA. Preincubation of the extracted membranes with palmitoyl-CoA and salts (KCI) for several minutes activates the enzyme and makes it increasingly insensitive to malonyl-CoA. Addition of malonyl-CoA to the preincubation reverses this desensitization. In albumin-containing media salts also decrease the binding of palmitoyl-CoA to albumin and stimulate carnitine palmitoyltransferase by increasing substrate availability in free solution. The reverse reaction shows accelerated desensitization by palmitoylcarnitine and resensitization by malonyl-CoA.