Hydrolysis of oligosaccharides by a fungal α‐galactosidase from fruiting bodies of a wild mushroom Leucopaxillus tricolor Leucopaxillus tricolor

摘要

A novel acidic α‐galactosidase (EC 3.2.1.22) designated as Leucopaxillus tricolor α‐galactosidase (LTG) has been purified to homogeneity from the fruiting bodies of L. tricolor to 855‐fold with a specific activity of 956?U?mg ?1 by the application of chromatography and gel filtration. The molecular mass of LTG was estimated to be 60?kDa as determined by both SDS–PAGE and by gel filtration. The purified enzyme was identified by LC‐MS/MS and four inner amino acid sequences were obtained. When 4‐nitrophenyl α‐D‐glucopyranoside (pNPGal) was used as substrate, the optimal pH and optimal temperature of LTG were pH 5.0 and 50?°C, respectively. The enzyme activity was strongly inhibited by Hg 2+ , Fe 3 , Cu 2+ , Cd 2+ , and Mn 2+ ions. The chemical modification agent N ‐bromosuccinimide (NBS) completely inhibited the enzyme activity of LTG, indicating the paramount importance of tryptophan residue(s) to its enzymatic activity. Besides, LTG displayed wide substrate diversity with activity toward a variety of substrates such as stachyose, raffinose, melibiose, locust bean gum, and guar gum. Given the good ability of degrading the non‐digestible and flatulence‐causing oligosaccharides, this fungus may become a useful source of α‐galactosidase for multiple applications.