INDUCTION OF BETA-OXIDATION ENZYMES AND MICROBODY PROLIFERATION IN ASPERGILLUS-NIDULANS

Aspergillus nidulans is able to grow on oleic acid as sole carbon sour ce. Characterization of the oleate-induced beta-oxidation pathway show ed the presence of the two enzyme activities involved in the first ste p of this catabolic system: acyl-CoA oxidase and acyl-CoA dehydrogenas e. After isopicnic centrifugation in a linear sucrose gradient, microb odies (peroxisomes) housing the beta-oxidation enzymes, isocitrate lya se and catalase were clearly resolved from the mitochondrial fraction, which contained fumarase. Growth on oleic acid was associated with th e development of many microbodies that were scattered throughout the c ytoplasm of the cells. These microbodies (peroxisomes) were round to e longated, made up 6% of the cytoplasmic volume, and were characterized by the presence of catalase. The beta-oxidation pathway was also indu ced in acetate-grown cells, although at lower levels; these cells lack ed acyl-CoA oxidase activity. Nevertheless, growth on acetate did not cause a massive proliferation of microbodies in A. nidulans.