Biosynthesis and identification of enzymes of the cellulase system of Trichoderma reesei
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The biosynthesis of cellulolytic enzymes by resting cells of T. reesei QM 9414 incubated in 17 mM potassium phosphate buffer, pH 6.0, and Q-Î²-D-glucopyranosy1-(172)Î±-D-glucopyranose was investigated. A maximum of 200 mi1liunits aryl-Î²-D-g1ucosidase, 9000 mi1liunits endo-l,4-Î²-D-glucanaseand 200 milliunits Avicelase per milliliter of culture supernate was produced after 24 hours of incubation; at that time, extracellular protein production reached a maximum of 0.5 mg/ml. Optimum enzyme yields were obtained with 3-4 mg dry weight cells/ml, and 1 nIDi 0-Î²-D-glucopyranosyl-(1->2)Î±-D-glucopyranose. Inclusion of metals, e.g., zinc, cobalt, manganous and ferrous ions enhanced enzyme production when glutamic acid was present, in which case aryl-Î²-D-glucosidase, endoglucanase and Avicelase activity were enhanced by 20, 100 and 40 percent, respectively. Under the same conditions asparagine enhanced only ary1-Î²-D-glucosidase activity. Some of the enzymic components of the cellulase system produced by T. reesei under these conditions were purified by ion exchange chromatography on DEAE-Sephadex A-50. Two cellobiohydrolases were isolated in pure form. One of these was identical to the previously isolated ce1lobiohydrolase D on the basis of amino acid composition carbohydrate content, electrophoretic mobility and ultraviolet spectrum. Similar data for the other cellobiohydrolase suggest that it represents an enzyme not previously identified. An endoglucanase was also isolated which, on the basis of its amino acid composition and electrophoretic mobility, appears similar to the previously identified Endoglucanase IV. More precise characterization of these enzymes is currently under investigation.
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