Purification and Characterization of a New Endo-β-1,3-glucanase Exhibiting a High Specificity for Curdlan for Production of β-1,3-Glucan Oligosaccharides

Endo-beta-1,3-glucanase (Endo23) was purified from a Trichoderma reesei GIMCC 3.498 fermentation broth using anion exchange and 2-stage size exclusion chromatography. Purification of 44.5x and a 12% recovery yield of enzyme activity were achieved. The Mw and isoelectric point were estimated to be 24 kDa and 3.85 using SDS-PAGE and IEF, respectively. The highest substrate specificity was observed for water-insoluble cundlan. The optimal conditions for hydrolyzing curdlan were pH 5.0 and 50 degrees C. The main hydrolytic products were glucobiose and glucotriose. Minor amounts of glucose and glucotetraose were detected. Hg2+, Fe2+, Fe3+, and Sn2+ inhibited the hydrolysis activity of Endo23 at 5 and 50 mM. K+ slightly promoted Endo23 activity. Endo23 belongs to the category EC3.2.1.39. The peptide sequences of Endo23 showed identity with conserved sequences that typically exist in beta-1,3-glucanases of the glycoside hydrolase family. The Endo23 sequence was partially similar to a hypothetical lignocellulase from Penicillium oxalicum 114-2.