FIG. 12.

Possible role of UCP3 to export excess mitochondrial fatty acids. Under conditions of high availability, fatty acid anions might accumulate in the mitochondrial matrix in two ways. One is through the flip-flop phenomenon (136). The other is through the carnitine palmitoyl transferase (CPT) system, followed by conversion of excess fatty acyl-CoAs to fatty acid anions and coenzyme A by mitochondrial thioesterase-1 (MTE-1) (289). In both cases, UCP3 would function to export the resultant trapped fatty acid anion protecting mitochondria from excess accumulation of fat and lipid peroxides. FAO, fatty acid oxidation.