Highly thermostable cellulase complex of an extremely thermophilic bacterium Anaerocellum thermophilumстатья

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[1] Highly thermostable cellulase complex of an extremely thermophilic bacterium anaerocellum thermophilum / D. F. Tikhomirov, V. V. Stolbova, V. A. Svetlichnyi, A. A. Klesov // Prikladnaya Biokhimiya i Mikrobiologiya. — 1992. — Vol. 28, no. 3. — P. 339–347. We have studied physico-chemical and biotechnological properties of cellulolytic enzymes: endo-1,4-beta-glucanase and a component limiting the rate of the insoluble cellulose hydrolysis from an extremely thermophilic anaerobic bacterium Anaerocellum thermophilum gen. nov., sp. nov. isolated from Kamchatka hot springs. The endoglucanase hydrolyzing soluble CM-cellulose over a wide range of pH 4-8 is not bound to other proteins in the culture broth and is characterized by a low affinity for cellulose (K-d = 0.06 L cntdot g-1). The enzyme is poorly inhibited by cellobiose by the incompetitive mechanism with K-i = 0.2 M. The half-inactivation period for the endoglucanase is 4 min at 95 degree and 150 min at 85 degree C. Elevation of growth temperasture from 68 to 75 degree C increases the thermal stability 1.5-fold. The component hydrolyzing insoluble cellulose (filter paper) at pH 5-7 is not incorporated into stable multienzyme complexes as well and is characterized by high thermal stability; its half-inactivation period at 85 degree C is 250 min. However, in contrast to the endoglucanase the component requires Ca-2+ ions (up to 10 mM) for exhibiting full stability. Its affinity for cellulose is by an order of magnitude higher than that of the endoglucanase.

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