Heterologous expression and characterization of a beta-1,6-glucanase from Aspergillus fumigatus

The cell wall of Candida albicans is composed of mannoproteins associated to glycan polymers. Most of these proteins are retained in this compartment through a phosphodiester linkage between a remnant of their glycosylphosphatidylinositol anchor and the beta-1,6-glucan polymer. A pure beta-1,6-glucanase is thus required in order to release them. In this paper, we report the expression/secretion by the yeast Yarrowia lipolytica of an Aspergillus fumigatus enzyme homologous to previously described beta-1,6-glucanases. The coding sequence was expressed under the control of a strong promoter and the recombinant enzyme was targeted to the secretory pathway using the signal sequence of a well-known major secretory protein in this host. Addition of a FLAG epitope at the C-terminus allowed its efficient purification from culture supernatant following batch adsorption. The purified enzyme was characterized as a beta-1,6-glucanase and was shown to be active on C. albicans cell walls allowing the release of a previously described cell wall protein.