The alpha-D-mannan core of a complex cell-wall heteroglycan of Trichoderma reesei is responsible for beta-glucosidase activation.

A heteroglycan responsible for the binding of the enzyme beta-1,4-D-glucosidase (EC 3.2.1.21) to fungal cell walls was isolated from cell walls of the filamentous fungus Trichoderma reesei. The heteroglycan, composed of mannose, galactose, glucose, and glucuronic acid, also activated beta-1,4-D-glucosidase, beta-1,4-D-xylosidase and N-acetyl-beta-1,4-D-glucosaminidase activity in vitro. The structural backbone of this heteroglycan was prepared by acid hydrolysis and gel filtration. The molecular structure of the core of the heteroglycan was determined by NMR studies as a linear alpha-1,6-D-mannan. The mannan core obtained by acid degradation stimulated the beta-glucosidase activity by 90%. Several glycosidases from Aspergillus niger were also activated by the T. reesei heteroglycan. The beta-glucosidase of Trichoderma was activated by mannan from Saccharomyces cerevisiae to a comparable extent.