Purification and partial characterization of a novel β-1,3-glucanase from the gut of sea cucumber Stichopus japonicus

For the first time, a β-1,3-glucanase was isolated from the gut of sea cucumber. The enzyme was purified to homogeneity by ammonium sulfate precipitation, ion exchange chromatography with diethylaminoethyl (DEAE)-Sepharose CL-6B, hydrophobic interaction chromatography with Butyl-Sepharose and preparative electrophoresis with polyacrylamide gel electrophoresis (PAGE). The molecular weight of the purified enzyme was estimated to be 37.5 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited optimum activity at pH 5.5 and 40 °C. The enzyme showed high pH stability within the range of pH 5.0–8.0 and thermostability up to 40 °C. The enzyme activity was markedly activated by Mn2+, whereas strongly inactivated by Cu2+ and Ag+. The Km and Vmax of the β-1,3-glucanase were 19.8 μg ml−1 and 2000 μg min−1 mg−1, respectively. The amino acid sequences of three segments of the purified enzyme were acquired by mass spectrometer method, which did not have any homology with previously described echinoderm β-1,3-glucanases, suggesting that it may be a novel member of echinoderm β-1,3-glucanase.