Intracellular Localization of Enzymes of Fatty Acid-β-Oxidation in the Alga Cyanidium caldarium

The intracellular distribution of enzymes, participating in the beta-oxidation of fatty acids in the eucaryotic alga Cyanidium has been studied. After separating the organelles from a crude homogenate on a linear flotation gradient, the enzymes enoyl-CoA hydratase, hydroxyacyl-CoA dehydrogenase, and thiolase were present in the mitochondrial fraction (density: 1.19 gram per cubic centimeter). Activity of an acyl-CoA synthetase was found in the mitochondrial fraction as well as in a band where mitochondrial membrane apparently had accumulated (density: 1.17 gram per cubic centimeter). None of these enzymes were present in the peroxisomes (density: 1.23 gram per cubic centimeter). Results from cell fractionation as well as properties of beta-oxidation enzymes indicate a mitochondrial location of fatty acid degradation also in the algae Galdieria sulphuraria and Cyanidioschyzon merolae.