日本根霉IFO5318胞外β-葡萄糖苷酶的纯化及部分特性

PURIFICATION AND SOME PROPERTISE OF EXTRACELLULAR β-GLUCOSIDASE FROM RHIZOPUS JAPONICUS IFO5318

采用硫酸铵沉淀及柱层析等步骤纯化了日本根霉IFO5318的β—葡萄糖苷酶,回收率为22％。该酶分子量约为4.0×10~5,由四个相同大小的亚基组成;最适反应温度55℃,最适反应pH5.5;对热较敏感,但能在较大的pH范围内保持稳定。用对硝基苯基—β-D-吡喃葡糖苷为底物,测得的K_m和V_(max)值分别为0.825mg·ml^(-1)和135.4μmol·min^(-1)·mg^(-1)。该酶对纤维二糖的水解能力最强,SDS、Fe^(3+)、Hg^2+)等对酶活力有抑制作用。

The β-glucosidase from Rhizopus japonicus IPO5318 was purified by Ammonium sulfate salting out and column chromatographies with the recovery of 22%. The molecular weight of the enzyme was about 4.0 × 105, consisting of four identical subunits; The optimum reaction temperature and pH for theβ-glucosidase were 55℃ and pH 5.5, respectively; While the enzyme was sensitive to heat, it could be stable at a wide range of pH. The Km and Fmax values of the enzyme were 0.825 mg· ml-1 and 135.4μmol · min-1 · mg-1, respectively, using p-Nitrophenyl-β-D-glucopyranoside as a substrate. Theβ-glucosidase exhibited strongest hydrolysis effect on cellobiose and some of its activity could be inhibited by SDS, Fe3+ and Hg2 + .