The Secretion of N-Acetylglucosaminidase during Germ-tube Formation in Candida albicans

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Abstract
N-Acetylglucosaminidase was induced by either N-acetylglucosamine or N-acetylmannosamine in several strains of C. albicans. Enzyme activity was not induced in a N-acetylglucosamine non-utilizing mutant which is unable to express the first 3 steps in the N-acetylglucosamine catabolic pathway. The enzyme, purified 500-fold, had a specific activity of 36.8 units (mg protein)-1 and catalyzed the hydrolysis of p-nitrophenyl-.beta.-n-acetylglucosamine, N,N''-diacetylchitobiose and N,N''N,''''-triacetylchitotriose. No activity was observed toward colloidal chitin, hyaluronic acid or mucin. The cellular distribution of N-acetylglucosaminidase was determined by measuring in situ enzyme activity before and after acid treatment of intact cells. N-Acetylglucosaminidase (80-88% of the total cellular activity) was rapidly secreted to the periplasm when the enzyme was induced either during yeast growth at 28.degree. C or germ-tube formation at 37.degree. C. Export of the enzyme from the periplasm into the medium was 4-fold greater during germ-tube formation, and after 6 h incubation the amount of enzyme released into the medium represented 70% of cell-associated enzyme activity.