1887

Abstract

Summary: The filamentous fungus excreted significant amounts of 1,3-β-glucanase, 1,6-β-glucanase and β-glucosidase activities when the culture medium was depleted of carbon sources. During starvation small amounts of intracellular 1,3-β- and 1,6-β-glucanase and β-glucosidase activities were also detected. Very low levels of β-glucanase activity remained bound to mycelium and some activity was found loosely attached to the cells and/or to water-soluble 1,3-β-/1,6-β-glucan adhering to the cell walls. During active growth intracellular 1,3-β-glucanase and mycelium-bound 1,3-β- and 1,6-β-glucanase activities were detected in small or trace amounts. During hyphal growth very low levels of 1,3-β- and 1,6-β-glucanase activities were also found to be weakly associated with the cells and/or with water-soluble β-glucan covering the hyphae. Cycloheximide inhibited the increase in intra- and extracellular 1,3-β- and 1,6-β-glucanase and β-glucosidase activities. This indicated that protein synthesis was involved in the intra- and extracellular appearance of these three enzyme activities in derepressed cells. The formation of the extracellular 1,3-β-glucanase, 1,6-β-glucanase and β-glucosidase activities was regulated by catabolite repression. 1,3-β- and 1,6-β-glucanase activities were uncompetitively inhibited and β-glucosidase activity noncompetitively inhibited by glucose and glucono-δ-lactone. Optimum pH and temperature values as well as thermal stabilities of the three extracellular enzyme activities were determined. Almost all of the β-glucosidase activity but only one-third of the extracellular 1,3-β- and 1,6-β-glucanase activities were found to bind to Con A-Sepharose. Under conditions of carbon limitation almost 90% of the extracellular 1,3-β-/1,6-β-glucan excreted during fungal growth was degraded by the extracellular β-glucanases.

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/content/journal/micro/10.1099/00221287-135-11-2847
1989-11-01
2019-10-23
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-135-11-2847
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