PURIFICATION AND CHARACTERIZATION OF AN ENDO-1,3-BETA-GLUCANASE FROM ASPERGILLUS-FUMIGATUS

An endo-1,3-beta-glucanase was purified from a cell wall autolysate of Aspergillus fumigatus. This beta-glucanase activity was associated wi th a glycosylated 74-kDa protein. Using a sensitive colorimetric assay and a high-performance anion-exchange chromatography with a pulsed el ectrochemical detector for product analysis, it was shown that the end oglucanase hydrolysed exclusively linear 1,3-beta-glucan chains, had a n optimum pH of 7.0 and an optimum temperature of 60 degrees C. A subs trate kinetic study gave a K-m value of 0.3 mg/ml for soluble (laminar in and laminari-oligosaccharides) and 1.18 mg/ml for insoluble (curdla n) 1,3-beta-glucan. Laminari-oligosaccharide degradation, analysed by HPLC, showed that the endoglucanase bind to the subtrate at several po sitions and suggested that the active site of the enzyme recognized fi ve glucose units linked by a 1,3-beta bond. The association of the pre sent endo-1,3-beta-glucanase with the cell wall of A. fumigatus sugges ts a putative role for this enzyme during cell-wall morphogenesis.