Doblin Sandai

By Doblin Sandai

The ICL1 gene, which encodes the glyoxylate cycle enzyme isocitrate lyase (Icl1), is required for the growth of Candida albicans on non-fermentable carbon sources and for this yeast to be virulent. The aim of this study is to test the stability of the Icl1 enzyme in response to glucose. Glucose was found to trigger the degradation of the ICL1 but the CaIcl1 was not destabilized by glucose. When CaIcl1 was expressed in Saccharomycess cerevisiae, it was not degraded in response to glucose, suggesting that CaIcl1 has lost the molecular signal that triggers destabilization in response to glucose. However, when ScIcl1 was expressed in C. albicans it was rapidly degraded in response to glucose indicating that C. albicans has retained the molecular apparatus for glucose-accelerated degradation of target proteins. ScIcl1 degradation was slowed in Caubi4/ubi4 in which ubiquitin-mediated protein turnover is reduced. Furthermore, the addition of putative ubiquitination site to the carboxyl-terminus of CaIcl1 led to the glucose-accelerated degradation of this protein. C. albicans has retained the apparatus for ubiquitin-mediated degradation of target protein in response to glucose. However, CaIcl1 has lost the Ubi-site that mediate glucose accelerated protein degradation, thereby allowing C. albicans to simultaneously assimilate alternative carbon sources and glucose.

Part of the book: Genital Infections and Infertility

By Doblin Sandai, Yasser Tabana and Rosline Sandai

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