Cellulose Digestion in the Wood-Eating Higher Termite, Nasutitermes takasagoensis (Shiraki) : Distribution of Cellulases and Properties of Endo-β-1, 4-glucanase

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β-Glucosidase [EC3. 2. 2. 21] and endo-β-1, 4-glucanase [EC3. 2. 1. 4] activities were measured in the wood-eating higher termite Nasutitermes takasagoensis. β-Glucosidase activity was present mainly in the selivary glands (66.7%) and midgut (22.2%), whereas endo-β-1, 4-glucanase activity was detected mainly in the midgut (90.1%). Specific activity of endo-β-1, 4-glucanase was also the highest in the midgut, indicating that cellulose is digested in the midgut. The major endo-β-1, 4-glucanase component of N. takasagoensis was purified from whole termites by gel filtration on Sephacryl S-200 HR, Superdex-75 and hydroxyapatite column chromatography. Subsequently, the endo-β-1, 4-glucanase activity from a crude midgut extract was eluted in an identical volume (Kd=0.68) to that from whole termites, suggesting the purified endo-β-1, 4-glucanase is idetical to that in the midgut. The molecular weight of the purified endo-β-1, 4-glucanase was 47kDa, and its specific activity was 1, 200 units/mg. The optimal pH and temperature were 5.8 and 65℃, respectively. The K_m and V_<max> values on carboxymethyl cellulose were 8.7 mg/ml and 2, 222 units/mg, respectively. The purified endo-β-1, 4-glucanase hydrolyzed cellopentaose to cellotriose and cellobiose, and cellotetraose to cellobiose and a trace of cellotriose and glucose, but cellotriose and cellobiose were not hydrolyzed. The activity and stability of pH and temperature of the purified endo-β-glucanase are prominent among those from various organisms.
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Cellulose Digestion in the Wood-Eating Higher Termite, Nasutitermes takasagoensis (Shiraki) : Distribution of Cellulases and Properties of Endo-β-1, 4-glucanase

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