This topic was to examine the impact of galactose or fructose upon the assimilation of secondary carbon sources by Candida albicans. C. albicans ICL1 gene is repressed upon addition of 2% galactose or fructose to lactate- and oleic acid-grown cells. Further studies on CaFOX2, CaFBP1 and CaMLS1 transcripts in response to galactose or fructose on assimilation of lactate and oleic acid resulted in repression of these genes. The CaICL1 gene, which encode the glyoxylate cycles enzymes isocitrate lyase are required for growth on non-fermentable carbon sources. However, the enzyme CaIcl1 was not destabilized by galactose, but was degraded in response to fructose. In contrast, S. cerevisiae Icl1 has retained the molecular apparatus of protein degradation in response to either galactose or fructose. Screening of ubiquitination site by http://www.ubpred.org/ showed that C. albicans lacks ubiquitination site in gluconeogenic and glyoxylate cycles enzymes as compare to S. cerevisiae. Addition of a putative S. cerevisiae ubiquitination site carboxy terminus of CaIcl1 led to galactose- accelerated degradation of this protein in C. albicans cell via a ubiquitin-dependent process. In the other hand, CaIcl prior to addition of ubiquitination site was degraded upon exposure to fructose; addition of S. cerevisiae ubiquitination site to CaIcl1 further increased the speed of protein degradation.
Part of the book: Candida Albicans