Endo-1,4-beta-Glucanases of the Anaerobic Bacterium Clostridium thermocellum St. No. 3 with a High Heat Stabilityстатья

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Дата последнего поиска статьи во внешних источниках: 20 апреля 2016 г.

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[1] Tikhomirov D. F., Stolbova V. V., Klyosov A. A. Endo-1,4-beta-glucanases of the anaerobic bacterium clostridium thermocellum st. no. 3 with a high heat stability // Prikladnaya Biokhimiya i Mikrobiologiya. — 1989. — Vol. 25, no. 1. — P. 48–54. After 115-hour cultivation of the anaerobic bacterium Clostridium thermocellum on 1% cellulose at 60.degree. C, 0.8 U/ml of endo-1,4-.beta.-glucanase was produced in the culture fluid. According to the evidence obtained in studies of thermal inactivation and confirmed by further fractionation of proteins, the enzyme is represented by two multiple forms dramatically differing in thermal stability. After purification the two forms were isolated: the main endoglucanase form responsible for 85% of the total filtrate activity with the half-life period 18th at 65.degree. C and 12 min at 75.degree. C and the minor form constituting 15% of the total activity and having considerable thermal stability with the half-life period 25 days at 65.degree. C, 15h at 75.degree. C and 10 min at 85.degree. C. The values are by an order of magnitude higher than those of the most heat stable fungal endoglucanases. Both forms of C. thermocellum endoglucanase are most active at pH 6.0 and 5.0, respectively. They need no Ca2+ ions, nor protection of SH-groups for catalysis, possess low affinity for the cellulose surface, and are not capable of effective hydrolysis of crystalline substrate in the absence of other cellulase complex components.

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