Isolation of a protease-resistant and pH-stable α-galactosidase displaying hydrolytic efficacy toward raffinose family oligosaccharides from the button mushroom Agaricus bisporus.

A 45-kDa monomeric acidic α-galactosidase with a specific activity of 193.12 units/mg was isolated from the fruiting bodies of Agaricus bisporus. Blast search of internal peptide sequences suggested that it is a member of GH family 27 and it is most similar to hypothetical protein AGABI2DRAFT_70106. The enzyme displayed maximal activity at pH 4.0 and 60°C, respectively. The enzyme remained stable within the pH range 2.0-9.0 but its activity was markedly suppressed in the presence of Cu2+, Hg2+, Fe3+ and Ag+ ions. It displayed resistance to α-chymotrypsin and neutral protease. Moreover, it manifested degradative activity toward both oligosaccharides and polysaccharides. The enzyme manifested Km values of 0.30mM, 10.65mM and 19.21mM, toward pNPGal, stachyose and raffinose respectively. These results suggest that Agaricus bisporus α-galactosidase is a promising candidate for elimination of raffinose oligosaccharides (RFOs) in biotechnological applications.