Abstract
In this study we attempted to determine the number of 2-enoyl-CoA hydratases involved in peroxisomal beta-oxidation. We therefore separated peroxisomal proteins from rat liver on several chromatographic columns and measured hydratase activities on the eluates with different substrates. The results indicate that rat liver peroxisomes contain two hydratase activities: (1) a hydratase activity associated with multifunctional protein 1 (MFP-1) (2-enoyl-CoA hydratase/delta 3, delta 2-enoyl-CoA isomerase/L-3-hydroxyacyl-CoA dehydrogenase) and (2) a hydratase activity associated with MFP-2 (17 beta-hydroxysteroid dehydrogenase/D-3-hydroxyacyl-CoA dehydrogenase/2-enoyl-CoA hydratase). MFP-1 forms and dehydrogenates L-3-hydroxyacyl-CoA species, whereas MFP-2 forms and dehydrogenates D-3-hydroxyacyl-CoA species. A portion of MFP-2 is proteolytically cleaved, most probably in the peroxisome, into a 34 kDa 17 beta-hydroxysteroid dehydrogenase/D-3-hydroxyacyl-CoA dehydrogenase and a 45 kDa D-specific 2-enoyl-CoA hydratase. Finally, the results confirm that MFP-1 is involved in the degradation of straight-chain fatty acids, whereas MFP-2 and its cleavage products seem to be involved in the degradation of the side chain of cholesterol (bile acid synthesis).