ISOLATION OF A BETA-GLUCOSIDASE BINDING AND ACTIVATING POLYSACCHARIDE FROM CELL-WALLS OF TRICHODERMA-REESEI

The extracellular β-glucosidase from the filamentous fungus Trichoderma reesei QM 9414 is mainly bound to the cell wall of the fungus and only partially released into the medium. Isolation of the cell walls and its hydrolysis by enzymatic treatment with Aspergillus niger cellulase released β-glucosidase, which appeared tightly associated with a cell wall polysaccharide. This polysaccharide was purified by gel filtration and ion exchange chromatography and was shown to consist of mannose, galactose, glucose, galacturonic acid and glucuronic acid. It was devoid of protein and phosphate. It reassociated both with extracellular β-glucosidase as well as β-glucosidase released from the fungus' cell wall. Addition of the polysaccharide to the β-glucosidase in vitro increased the enzyme's activity against 4-nitrophenyl-β-glucoside twofold. These findings suggest, that the isolated polysaccharide functions as an "anchor glycan" for the β-glucosidase in Trichoderma reesei. © 1990 Springer-Verlag.