Peroxisomal β‐oxidation system of Candida tropicalis

1. A multifunctional protein from oleate-grown cells of Candida tropicalis has been purified and partially characterized. A simple two-step purification has been developed involving ion-exchange chromatography followed by dye-ligand chromatography on blue Sepharose CL-6B. Homogeneous enzyme with a subunit Mr of 102000 is obtained in 60% yield. The native relative molecular mass, determined by three different methods, yielded values which suggest that the enzyme is dimeric. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of the purified protein revealed a single polypeptide band and reverse-phase high-performance liquid chromatography indicated a single component suggesting that this protein may consist either of two identical or very similar subunits. 2. Three β-oxidation activities, enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase and 3-hydroxyacyl-CoA epimerase, co-purified with this protein. The ratio of the three β-oxidation enzyme activities remained constant during purification and was unchanged by additional chromatographic methods (adsorption and affinity chromatography), thus indicating the multifunctional nature of this protein. Enzymatic staining of the purified protein for 3-hydroxyacyl-CoA dehydrogenase and epimerase, following electrophoresis in a polyacrylamide density gradient, further supported the multifunctionality of this protein. 3. After isopycnic centrifugation of a particulate fraction from oleate-grown cells in a linear sucrose gradient the activities of all individual β-oxidation enzymes cosedimented with catalase and with the glyoxylate bypass enzymes. This result demonstrated the peroxisomal localization of the multifunctional enzyme. 4. The relationship of this multifunctional protein to the two bifunctional β-oxidation enzymes isolated from peroxisomes of rat liver and from glyoxysomes of cucumber seeds is discussed.