Exoglucanase (EC 18.104.22.168) was partially purified from Aspergillus niger. The enzyme was stable at room temperature in the pH range of 4.0-6.0 for 24h, with the optimum at 5.5. The enzyme had an optimum temperature of 50°C and a t1/2 at 65°C was 70min. Km and Vmax values were found to be 55.5mg/ml and 0.9μM/min, respectively. Glycerol protected the enzyme from inactivation on storage and from denaturation due to freezing and thawing. The effect of the sulfhydryl group reagents tested suggested the presence of -SH on the active site of the enzyme. Mn2+ and Co2+ were good activators of the enzyme, whereas Hg2+ and Pb2+ were potent inhibitors. The enzyme was a metalloprotein, or it requires certain metal ions for activation.
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