Abstract
The most frequently isolated human fungal pathogen is Candida albicans which is responsible for about 50% of all Candida infections. In healthy individuals, this organism resides as a part of the normal microbiota in equilibrium with the host. However, under certain conditions, particularly in immunocompromised patients, this opportunistic pathogen adheres to host cells causing serious systemic infections. Thus, much effort has been dedicated to the study of its physiology with emphasis on factors associated to pathogenicity. A representative analysis deals with the mechanisms of glycoprotein assembly as many cell surface antigens and other macromolecules that modulate the immune system fall within this chemical category. In this regard, studies of the terminal protein glycosylation stage which occurs in Golgi vesicles has led to the identification of nucleotidases that convert glycosyltransferase-generated dinucleotides into the corresponding mononucleotides, thus playing a double function: their activity prevent inhibition of further glycosyl transfer by the accumulation of dinucleotides and the resulting mononucleotides are exchanged by specific membrane transporters for equimolecular amounts of sugar donors from the cytosol. Here, using a simple protocol for protein separation we isolated a bifunctional nucleotidase from C. albicans active on GDP and UDP that was characterized in terms of its molecular mass, response to bivalent ions and other factors, substrate specificity and affinity. Results are discussed in terms of the similarities and differences of this nucleotidase with similar counterparts from other organisms thus contributing to the knowledge of a bifunctional diphosphatase not described before in C. albicans.
Highlights
Candida species are the most frequent cause of nosocomial fungal infections in U.S hospitals (Edmond et al 1999; Wisplinghoff et al 2004)
To learn more about nucleotidases in this pathogen, here we report the purification to homogeneity and partial characterization of a membrane-bound enzyme whose properties are compatible with a bifunctional nucleoside diphosphatases (NDPases) active on GDP and UDP
In silico search of UDPase protein in C. albicans met with failure indicating that genes/proteins associated with the enzyme have not yet been annotated in these organisms
Summary
Candida species are the most frequent cause of nosocomial fungal infections in U.S hospitals (Edmond et al 1999; Wisplinghoff et al 2004). The fungal CW exhibits a characteristic composition consisting mainly of b-glucans, chitin and glycoproteins (Gow et al 2017; Garcia-Rubio et al 2020). These components do not exist in humans and represent a potential target for antimicrobial drugs. On this basis, interest of this laboratory has dealt with the search of surface antigenic components such as glycoproteins and other components in human pathogenic fungi such as Candida and Sporothrix species. This has led us to the analysis of glycosyl transferases and glycosidases that participate in glycoprotein biosynthesis (Mora-Montes et al 2009; López-Romero et al 2011) and most recently on enzymes that participate in the final stages of glycoprotein assembly such as nucleoside diphosphatases (NDPases)
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