Induction of β-oxidation enzymes and microbody proliferation in Aspergillus nidulans

Abstract

Aspergillus nidulans is able to grow on oleic acid as sole carbon source. Characterization of the oleate-induced beta-oxidation pathway showed the presence of the two enzyme activities involved in the first step of this catabolic system: acyl-CoA oxidase and acyl-CoA dehydrogenase. After isopicnic centrifugation in a linear sucrose gradient, microbodies (peroxisomes) housing the beta-oxidation enzymes, isocitrate lyase and catalase were clearly resolved from the mitochondrial fraction, which contained fumarase. Growth on oleic acid was associated with the development of many microbodies that were scattered throughout the cytoplasm of the cells. These microbodies (peroxisomes) were round to elongated, made up 6% of the cytoplasmic volume, and were characterized by the presence of catalase. The beta-oxidation pathway was also induced in acetate-grown cells, although at lower levels; these cells lacked acyl-CoA oxidase activity. Nevertheless, growth on acetate did not cause a massive proliferation of microbodies in A. nidulans.

A Eukaryote without Catalase-Containing Microbodies: Neurosporacrassa Exhibits a Unique Cellular Distributionof Its Four Catalases

“…In line with this perception was the observation that Aspergillus strains do contain peroxisomal catalase, since this genus exploits the typical acyl-CoA oxidase for the first step in peroxisomal ␤-oxidation (32,51). This difference in catalase localization is remarkable in so far as Neurospora and Aspergillus are both members of the subphylum Pezizomycotina.…”

Multiple Catalase Genes Are Differentially Regulated in Aspergillus nidulans

“…Second, our preliminary cell fractionation experiments using cell extracts from catA catB double mutant grown for 18 h showed that at least 20% of the total CatC activity is contained within the subcellular particle pellet, along with high activity levels of the peroxisomal marker isocitrate lyase (41) and the mitochondrial marker fumarase. Third, a catalase activity has been cytochemically localized in microbodies from young growing hyphae, and cosedimentation of catalase activity and peroxisome marker enzymes has also been shown in A. nidulans (42). It is unlikely that the reported peroxisome-associated catalase (42) corresponds to CatA, CatB, or CatD.…”

The activity of the glyoxylate cycle in peroxisomes of Candida albicans depends on a functional β-oxidation pathway: evidence for reduced metabolite transport across the peroxisomal membrane

“…In the C. albicans genome, single genes exist for Icl1 (orf19.6844), Mls1 (orf19.4833) and citrate synthase (orf19.4393), whereas there are three encoding malate dehydrogenase (orf19.7481, orf19.4602 and orf19.5223) and two for aconitase (orf19.6385 and orf19.6632). Studies in fungi have shown that the key enzymes of the glyoxylate cycle, Icl1 and Mls1, are often compartmentalized in peroxisomes, the other enzymic steps being extra-peroxisomal (either cytosolic or mitochondrial) (Hikida et al, 1991;Maeting et al, 1999;Tanaka & Ueda, 1993;Titorenko et al, 1998;Valenciano et al, 1996). Saccharomyces cerevisiae seems to be an exception to this rule: Icl1 is a cytosolic enzyme (McCammon et al, 1990) and Mls1 is localized either to the peroxisome or to the cytosol depending on the growth conditions (Kunze et al, 2002).…”