An endoglucanase (1,4-beta-D-glucan glucanohydrolase, EC 220.127.116.11) from the thermophilic anaerobe Clostridium thermocellum was purified to apparent homogeneity without the use of denaturants. No carbohydrate is associated with the endoglucanase. A molecular mass of 76,000 Da was determined by SDS/PAGE. The optimal pH is 7.0 and the enzyme is isoelectric at pH 5.05. The enzyme has a temperature optimum of 70 degrees C and retains approx. 50% of its activity after 48 h at 60 degrees C. Hydrolysis of CM-cellulose takes place with a rapid decrease in viscosity but a slow liberation of reducing sugars, indicating an endoglucanase type of activity. The endoglucanase shows little ability to hydrolyse highly ordered cellulose. Cellobiose inhibits whereas Mg2+ and Ca2+ stimulate the activity. The enzyme is completely inactivated by 1 mM-Hg2+ and is inhibited by a thiol-blocking reagent.
Purification and characterization of a new endoglucanase from Clostridium thermocellum
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M P M Romaniec, U Fauth, T Kobayashi, N S Huskisson, P J Barker, A L Demain; Purification and characterization of a new endoglucanase from Clostridium thermocellum. Biochem J 1 April 1992; 283 (1): 69–73. doi: https://doi.org/10.1042/bj2830069
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