Cell wall studies of Histoplasma capsulatum and Blastomyces dermatitidis using autologous and heterologous enzymes

Abstract

Enzymes capable of hydrolyzing cell walls of B. dermatitidis and chemotypes I and II of H. capsulatum were prepared in the laboratory or obtained from commercial sources. They included chitinases, β-1,3-glucanases, β-1,6-glucanase, and Pronase. Monosaccharides and disaccharides of glucose released from the cell walls by the enzymes were determined qualitatively by paper and gas-liquid chromatography, and monosaccharides were quantitated by the latter technique as well. An enzyme system isolated from Streptomyces sp. containing both chitinase and glucanase released maximum amounts of glucose and N-acetylglucosamine from the cell walls of H.capsulatum chemotype I. A chitinase preparation, free of glucanase, from Serratia marcescens released only chitobiose and N-acetylglucosamine from chemotype I cell walls, but the total quantity of N-acetylglucosamine released was about 60% less than that released by the Streptomyces system. A β-1,3-glucanase from Bacillus circulans hydrolyzed the cell walls of H. capsulatum chemotype I, but a β-1,6-glucanase failed to release glucose from the same walls. Autolytic enzymes, viz., β-1,3-glucanases and several glycosidases, were detected as constitutive enzymes in both yeast and mycelial phases of B. dermatitidis and H. capsulatum chemotypes I and II. No difference in the amount of activity was found between cell sap and culture filtrate preparations. The β-glucanases prepared from the Histoplasma and Blastomyces strains were active on the cell walls of the yeast phases of H. capsulatum chemotypes I and II, releasing laminaribiose and glucose, but were essentially inactive on the cell walls of B. dermatitidis. Chitinase, β-1,6-glucanase, α-glucanase, and α-glucosidase activities were absent from these fungal enzyme preparations.