Biochemical characterization of a 27 kDa 1,3-β-D-glucanase from Trichoderma asperellum induced by cell wall of Rhizoctonia solani

Trichoderma asperellum produces two extracellular 1,3-beta-D-glucanase upon induction with cell walls from Rhizoctonia solani. A minor 1,3-beta-D-glucanase was purified to homogeneity by ion exchange chromatography on Q-Sepharose and gel filtration on Sephacryl S-100. A typical procedure provided 13.8-fold purification with 70% yield. SOS-PAGE of the purified enzyme showed a single protein band of molecular weight 27 kDa. The enzyme exhibited optimum catalytic activity at pH 3.6 and 45 degrees C. It was thermostable at 40 degrees C, and retained 75% activity after 60 min at 45 degrees C. The K-m and V-max values for 1,3-beta-D-glucanase, using laminarin as substrate, were 0.323 mg ml(-1) and 0.315 U min(-1), respectively. The enzyme was strongly inhibited by Hg2+ and SDS. The enzyme was only active toward glucans containing beta-1,3-linkages. Peptide sequences showed similarity with two endo-1,3(4)-beta-D-glucanases from Aspergillus fumigatus Af293when compared against GenBank non-redundant database. (C) 2011 Elsevier Ltd. All rights reserved.