Studies on the activation in vitro of carnitine palmitoyltransferase I in liver mitochondria from normal, diabetic and glucagon-treated rats.

The activation of overt carnitine palmitoyltransferase activity that occurs when rat liver mitochondria are incubated at near-physiological temperatures and ionic strengths was studied for mitochondria obtained from animals in different physiological states. In all instances, it was found to be due exclusively to an increase in the catalytic capacity of the enzyme and not to an increase in affinity of the enzyme for palmitoyl-CoA. The enzyme in mitochondria from fed animals always showed a larger degree of activation than that in mitochondria from starved animals. This was the case even for mitochondria (e.g. from fed diabetic animals) in which the kinetic characteristics of carnitine palmitoyltransferase were more similar to those for the enzyme in mitochondria from starved rats. Glucagon treatment of rats before isolation of the mitochondria did not affect the characteristics either of the kinetic parameters of overt carnitine palmitoyltransferase or of its activation in vitro.