Carnitine-acyltransferase activity assayed with acetyl-CoA, octanoyl-CoA, or palmitoyl-CoA is associated with the mitochondrial but not with the peroxisomes of mung-bean hypocotyls. Using mitochondria as an enzyme source, a half-maximal reaction rate is obtained with a palmitoyl-CoA concentration approximately twice that required with acetyl-CoA. In the presence of a saturating acetyl-CoA concentration the carnitine-acyltransferase activity is not enhanced by palmitoyl-CoA as additional substrate. However, palmitoylcarnitine is formed in addition to acetylcarnitine, and the formation of acetylcarnitine is competitively inhibited by palmitoyl-CoA. It is concluded that the mitochondria of mung-bean hypocotyls possess a carnitine acyltransferase of broad substrate specificity with respect to the chainlength of the acyl-CoA and that the demonstration of a carnitine-palmitoyltransferase activity in plant mitochondria does not indicate the presence of a specific carnitine long-chain acyltransferase.
展开▼
