The role of carnitine and carnitine acyltransferase in biological acetylations and fatty acid synthesis.

The effect of (-)-carnitine on the conversion of citratel-r4C and pyruvate-2J4C to 14C02 and either 14C-fatty acids or 14C-acetylsulfanilamide was studied in pigeon liver homogenates. Carnitine stimulated the conversion of pyruvate-2-W to fatty acids and acetylsulfanilamide, but had no effect on citrate. In the fasted state both fatty acid synthesis and citrate cleavage enzyme activity were decreased, whereas the conversion of pyruvate-2-14C to 14C-acetylsulfanilamide and carnitine acyltransferase activity were increased. (+)-Camitine, a competitive inhibitor of carnitine acyltransferase, decreased the conversion of pyruvate-2J4C to 14C-acetylsulfanilamide. It was concluded from calculations of W02 and 14C-fatty acids derived from citrate-lJ4C and pyruvate-2J4C that the major pathway of supply of acetyl groups to the extramitochondrial portion of the cell is an indirect one via citrate and the citrate cleavage enzyme, but that a direct pathway via carnitine acyltransferase does exist. A role of carnitine acyltransferase in biological acetylations is discussed.