Characterization of an unglycosylated low molecular weight 1,4-β-glucan-glucanohydrolase ofTrichoderma reesei

Abstract

A low molecular weight endoglucanase (1,4-β-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: M_r 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°C. The activitity of this endoglucanase gave a strong increase in CMC-fluidity with only a small release of reducting 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 toward crystalline cellulose (Avicel) or xylan. The endoglucanase is not a glycoprotein.