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

• Published in: Microbiology (Society for General Microbiology) 2008-10, Vol.154 (10), p.3061-3072
• Main Authors: Piekarska, Katarzyna, Hardy, Guy, Mol, Els, van den Burg, Janny, Strijbis, Karin, van Roermund, Carlo, van den Berg, Marlene, Distel, Ben
• Format: Article
• Language: English
• Subjects: Candida albicans
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.2008/020289-0

1 Department of Medical Biochemistry, Academic Medical Center, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands 2 Department of Genetic Metabolic Diseases, Academic Medical Center, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands Correspondence Ben Distel b.distel{at}amc.uva.nl The glyoxylate cycle, a metabolic pathway required for generating C 4 units from C 2 compounds, is an important factor in virulence, in both animal and plant pathogens. Here, we report the localization of the key enzymes of this cycle, isocitrate lyase (Icl1; EC 4.1.3.1) and malate synthase (Mls1; EC 2.3.3.9 ), in the human fungal pathogen Candida albicans . Immunocytochemistry in combination with subcellular fractionation showed that both Icl1 and Mls1 are localized to peroxisomes, independent of the carbon source used. Although Icl1 and Mls1 lack a consensus type I peroxisomal targeting signal (PTS1), their import into peroxisomes was dependent on the PTS1 receptor Pex5p, suggesting the presence of non-canonical targeting signals in both proteins. Peroxisomal compartmentalization of the glyoxylate cycle is not essential for proper functioning of this metabolic pathway because a pex5 / strain, in which Icl1 and Mls1 were localized to the cytosol, grew equally as well as the wild-type strain on acetate and ethanol. Previously, we reported that a fox2 / strain that is completely deficient in fatty acid β -oxidation, but has no peroxisomal protein import defect, displayed strongly reduced growth on non-fermentable carbon sources such as acetate and ethanol. Here, we show that growth of the fox2 / strain on these carbon compounds can be restored when Icl1 and Mls1 are relocated to the cytosol by deleting the PEX5 gene. We hypothesize that the fox2 / strain is disturbed in the transport of glyoxylate cycle products and/or acetyl-CoA across the peroxisomal membrane and discuss the possible relationship between such a transport defect and the presence of giant peroxisomes in the fox2 / mutant. Abbreviations: Icl1, isocitrate lyase; Mls1, malate synthase; PEX, peroxisome biogenesis gene/protein; PTS1, peroxisomal targeting signal 1; TCA, tricarboxylic acid Present address: University of Manchester, The Michael Smith Building A1030, Oxford Road, Manchester M13 9PT, UK.