CARNITINE ACETYLTRANSFERASE IS NOT A CYTOSOLIC ENZYME IN RAT-HEART AND THEREFORE CANNOT FUNCTION IN THE ENERGY-LINKED REGULATION OF CARDIACFATTY-ACID OXIDATION

The subcellular location of cardiac carnitine acetyltransferase (CAT) was investigated by measuring the release of carnitine acetyltransfera se and of marker enzymes hom isolated rat myocytes permeabilized with digitonin, Additionally, the carnitine acetyltransferase activity expo sed to the cytosolic compartment was quantified. The results indicate that soluble acetyl transferase is not present in the cytosol, and tha t only 5% of the cellular carnitine acetyltransferase activity is posi tioned to catalyse the formation of cytosolic acetyl coenzyme A. This situation mal;es it unlikely that the energy-linked regulation of card iac fatty acid oxidation proceeds by mechanisms which require the conv ersion of acetylcarnitine to acetyl coenzyme A in the cytosol. (C) 199 8 Academic Press.