Abstract
The effect of (-)-carnitine on the conversion of citrate-1-14C and pyruvate-2-14C to 14CO2 and either 14C-fatty acids or 14C-acetylsulfanilamide was studied in pigeon liver homogenates. Carnitine stimulated the conversion of pyruvate-2-14C 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. (+)-Carnitine, a competitive inhibitor of carnitine acyltransferase, decreased the conversion of pyruvate-2-14C to 14C-acetylsulfanilamide. It was concluded from calculations of 14CO2 and 14C-fatty acids derived from citrate-1-14C and pyruvate-2-14C 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.
Highlights
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
That carnitine stimulated the incorporation into fatty acids of those compounds that give rise to acetyl-Coa within the mitochondria [9, 10]
Fritz and Schultz [13] have suggested that carnitine acyltransferase may play a role in the translocation of activated acetyl groups out of the mitochondria. These investigations provide evidence that is consonant with the hypothesis that acetyl-CoA formed within the mitochondria may be converted to acetylcarnitine in the presence of carnitine and carnitine acyltransferase
Summary
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 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
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