Short-chain fatty acid activation in rat liver a new assay procedure for the enzymes and studies on their intracellular localization

Abstract

1. Acetyl-CoA synthetase (acetate:CoA ligase (AMP), EC 6.2.1.1) and mediumchain acyl-CoA synthetase (acid: CoAligase (AMP), EC 6.2.1.2) have been studied in rat-liver homogenate and cellular subfractions. A new assay procedure for the enzymes has been worked out. The acyl-CoA formed is transformed into acylcarnitine by excess amounts of acetyl-CoA: carnitine acetyl transferase (EC 2.3.1.7) in the presence of radioactive carnitine. 2. With differential centrifugation of rat-liver homogenate, it has been shown that the medium-chain acyl-CoA synthetase is exclusively localized in mitochondria, and by subfractionation of the mitochondria we found that the enzyme is confined to the matrix. 3. The acetyl-CoA synthetase apparently has a bimodal intracellular localization, the enzyme being localized both in mitochondria and in the particle-free supernatant. The mitochondrial part is confined to the matrix.