Characterization of an unglycosylated low molecular weight 1,4-beta-glucan-glucanohydrolase of Trichoderma reesei.

A low molecular weight endoglucanase (1,4-beta-glucan glucanohydrolase E.C.3.2.1.4) was purified to homogeneity by a two-step procedure from 7 day old culture filtrates of Trichoderma reesei. The endoglucanase was obtained by BioGel A 0.5 m gel chromatography followed by preparative PAGIF. The purified endoglucanase was homogeneous upon titration curve separation. Enzyme characteristics were: Mr 25 kDa, pI 7.5. The amino acid composition is predominantly neutral (mainly glycine). The N-terminus is arginine. The pH-optimum for this endoglucanase was 5.8 and its optimal temperature was at 52 degrees C. The activity of this endoglucanase gave a strong increase in CMC-fluidity with only a small release of reducing sugars. The endoglucanase was 0.2% of total culture medium protein content. The reducing sugars upon CMC digestion were G1-G4. The enzyme had no specificity towards crystalline cellulose (Avicel) or xylan. The endoglucanase is not a glycoprotein.