Mode of action of exo-beta-1,3-glucanase from Trichoderma pseudokoningii TM37 on various beta-D-glucans

Two or three different beta-1,3-glucanases are present in Trichoderma pseudokoningii TM37 culture broth. One of these enzymes, EP-1, was purified from a crude enzyme preparation. It seemed to be a single polypeptide with a high molecular weight (>200 kDa by SDS-PAGE) and a pI of 7.0. The optimum pH and temperature for laminarin degradation were 5.0 and 60 degrees C, respectively. EP-1 hydrolyzed beta-1,3-glucans such as pachyman and laminarin to produce almost only glucose. From these results and the hydrolysis patterns of laminarioligosaccharides, EP-1 appeared to be a typical exo-beta-1,3-glucanase releasing only glucose from the non-reducing end of beta-1,3-glucans. However, EP-1 also hydrolyzed beta-glucans containing beta-1,3- and beta-1,4-linkages such as barley glucan, or beta-1,3- and beta-1,6-linkages such as yeast glucan and laminarin, and besides glucose produced various mixed oligosaccharides with different linkages from these substrates. In this respect, though EP-1 is an exo-enzyme, it could hydrolyze internal glycosydic linkages in the main polysaccharide chain of mixed glucans with different linkages.