Purification and Characterization of an Endo-(1,3)-β- d -Glucanase from Trichoderma longibrachiatum

Abstract

A laminarinase [endo-(1,3)-β- d -glucanase] has been purified from Trichoderma longibrachiatum cultivated with d -glucose as the growth substrate. The enzyme was found to hydrolyze laminarin to oligosaccharides varying in size from glucose to pentaose and to lesser amounts of larger oligosaccharides. The enzyme was unable to cleave laminaribiose but hydrolyzed triose to laminaribiose and glucose. The enzyme cleaved laminaritetraose, yielding laminaritriose, laminaribiose, and glucose, and similarly cleaved laminaripentaose, yielding laminaritetraose, laminaritriose, laminaribiose, and glucose. The enzyme cleaved only glucans containing β-1,3 linkages. The pH and temperature optima were 4.8 and 55°C, respectively. Stability in the absence of a substrate was observed at temperatures up to 50°C and at pH values between 4.9 and 9.3. The molecular mass was determined to be 70 kilodaltons by sodium dodecyl sulfate-12.5% polyacrylamide gel electrophoresis, and the pI was 7.2. Enzyme activity was significantly inhibited in the presence of HgCl 2 , MnCl 2 , KMnO 4 , and N -bromosuccinimide. The K m of the enzyme on laminarin was 0.0016%, and the V max on laminarin was 3,170 μmol of glucose equivalents per mg of the pure enzyme per min.