Carnitine acyltransferase and acyl-coenzyme A hydrolase activities in human liver. Quantitative analysis of their subcellular localization.
The subcellular localizations of carnitine acyltransferase and acyl-CoA hydrolase activities with different chain-length substrates were quantitatively evaluated in human liver by fractionation of total homogenates in metrizamide density gradients and by differential centrifugation. Peroxisomes were found to contain 8-37% of the liver acyltransferase activity, the relative amount depending on the chain length of the substrate. The remaining activity was ascribed to mitochondria, except for carnitine octanoyltransferase, for which 25% of the activity was present in microsomal fractions. In contrast with rat liver, where the activity in peroxisomes is very low or absent, human liver peroxisomes contain about 20% of the carnitine palmitoyltransferase. Short-chain acyl-CoA hydrolase activity was found to be localized mainly in the mitochondrial and soluble compartments, whereas the long-chain activity was present in both microsomal fractions and the soluble compartment. Particle-bound acyl-CoA hydrolase activity for medium-chain substrates exhibited an intermediate distribution, in mitochondria and microsomal fractions, with 30-40% of the activity in the soluble fraction. No acyl-CoA hydrolase activity appears to be present in human liver peroxisomes.
D000217:Acyltransferases / Q000378:metabolism*; D002333:Carnitine Acyltransferases / Q000378:metabolism*; D002498:Centrifugation; D002500:Centrifugation, Isopycnic; D006801:Humans; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology*; D010170:Palmitoyl-CoA Hydrolase / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000378:metabolism*
D000217:Acyltransferases; D002333:Carnitine Acyltransferases; D013869:Thiolester Hydrolases; D010170:Palmitoyl-CoA Hydrolase