Carnitine-acylcarnitine translocase

Carnitine-acylcarnitine translocases are responsible for transporting both carnitine and carnitine-fatty acid complexes into and out of the mitochondria, across the inner mitochondrial membrane.

Function

This enzyme is required as fatty acids cannot cross the mitochondrial membranes without assistance. The fatty acid is firstly bound to CoA to cross the external mitochondrial membrane. It then switches the CoA for carnitine by the use of the enzyme carnitine palmitoyltransferase I. The complex then uses facilitated diffusion by Carnitine-acylcarnitine translocase to enter the mitochondrial matrix. Here, the acyl-cartinine complex is disrupted by carnitine palmitoyltransferase II and the fatty acid rebinds to CoA. Carnitine then diffuses back across the membrane by a second carnitine-acylcarnitine translocase into the inter-mitochondrial membrane space. This is the carnitine shuttle system.

Clinical significance

A disorder is associated with carnitine-acylcarnitine translocase deficiency. This disorder prevents the shuttle-like action of carnitine from assisting fatty acids across the mitochondrial membrane and therefore there is decreased fatty acid metabolism. The result of this is an increased number of fat droplets within muscles and liver, decreased tolerance to long term exercise, inability to fast for more than a few hours, muscle weakness and wasting, strong acidic smell on breath (due to protein breakdown)