Full text loading...
Abstract
Addition of tunicamycin to the culture medium of growing Saccharomyces cerevisiae protoplasts or cells resulted in the formation of a modified exo-1,3-β-d-glucanase which was detectable in both extracellular and intracellular fractions. This modified enzyme had a lower molecular weight than the native form and did not bind to concanavalin A. The activation energy and K m values of both enzyme forms were identical. Antibodies raised against the native protein readily precipitated the exo-1,3-β-d-glucanase produced after tunicamycin treatment. The latter enzyme was comparable, in terms of molecular size and lack of affinity for concanavalin A. to the β-d-glucanase obtained by treatment of the native form with endoglycosidase H; both lacked the carbohydrate moiety present in the native enzyme. The exo-1,3-β-d glucanase obtained in the presence of the antibiotic was more sensitive to variations in temperature and pH than both endoglycosidase H-treated and non-treated enzymes. Our results suggest that the carbohydrate moiety, if not necessary for exo-1,3-β-d-glucanase secretion, may play a role in the conformation of the protein and in stabilizing the enzymic activity.
- Received:
- Revised:
- Published Online: