No abstract

An endoglucanase (1, 4-b-D glucan glucanohydrolase, EC 3.2.1.4) which was catalytically more active and exhibited higher affinity towards barley b-glucan, xyloglucan and lichenin as compared to carboxymethylcellulose (CMC) was purified from Aspergillus terreus strain AN 1 following ion-exchange and hydrophobic interaction chromatography and gel filtration. The purified enzyme (40-fold) that apparently lacked a cellulose-binding domain showed a specific activity of 60 lmol mg -1 protein -1 against CMC. The purified enzyme had a molecular weight of 78 and 80 KDa as indicated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and gel filtration, respectively, and a pI of 3.5. The enzyme was optimally active at temperature 60°C and pH 4.0, and was stable over a broad range of pH (3.0-5.0) at 50°C. The endoglucanase activity was positively modulated in the presence of Cu 2? , Mg 2? , Ca 2? , Na ? , DTT and mercaptoethanol. Endoglucanase exhibited maximal turn over number (K cat ) and catalytic efficiency (K cat/km ) of 19.11 9 10 5 min -1 and 29.7 9 10 5 mM -1 min -1 against barley b-glucan as substrate, respectively. Hydrolysis of CMC and barley b-glucan liberated cellobiose, cellotriose, cellotetraose and detectable amount of glucose. The hydrolysis of xyloglucan, however, apparently yielded positional isomers of cellobiose, cellotriose and cellotetraose as well as larger oligosaccharides.