Exo-1,3-beta-glucanase activity in Candida albicans: effect of the yeast-to-mycelium transition.

Yeast cells of Candida albicans 1001 produced glucan-hydrolysing activity, most of which was due to an exo-1,3-beta-glucanase. The enzyme was periplasmically located; it could be found in culture medium samples, and was secreted by protoplasts when cultured under regeneration conditions. In contrast to most yeast exoglucanases, this enzyme was practically inactive against p-nitrophenyl-beta-D-glucoside, hydrolysis of this substrate being carried out by a beta-glucosidase located inside the cytoplasmic membrane and not secreted to the external medium. Supernatant fluids from cell-free extracts reached their maximum glucanase level after several days at 0 degrees C, suggesting that the active enzyme was formed from an inactive precursor. Glucanase activity substantially decreased and sometimes disappeared from the cells when the yeast-to-mycelium transition was induced, but a significant (though lesser) reduction was also observed in yeast cells incubated in the same medium under conditions (temperature, cell concentration) that did not lead to formation of hyphae. It is suggested that C. albicans exo-1,3-beta-glucanase may not be necessary for mycelial growth.