Characterization of WdChs3p, a class III chitin synthase, of Wangiella (Exophiala) dermatitidis, overexpressed in Saccharomyces cerevisiae.

The class III chitin synthase (WdChs3p) of the fungal pathogen of humans Wangiella dermatitidis is expressed differentially under stress growth conditions and, together with WdChs2p, it contributes to virulence. However, because this fungus produces four other chitin synthases, and a quadruple disruption strain with only WdChs3p activity has not been derived, we characterized this enzyme further after heterologous expression of the WdCHS3 cDNA under the regulation of the inducible GAL1 promoter in Saccharomyces cerevisiae. In contrast to our prior conclusions about the zymogenic nature of WdChs3p produced in W. dermatitidis, the enzyme expressed in yeast had a non-zymogenic activity, that is, an activity not potentiated by controlled proteolysis. Nonetheless, other characteristics of WdChs3p activity expressed in yeast were similar to those of the enzyme from its parent, including being stable over a broad range of pH and temperature values, which should facilitate attempts to purify this unique chitin synthase and better define its structure.