Takahashi N, Mizuno F, Takamori K
Infect Immun. 1985 Jan;47(1):271-6. doi: 10.1128/iai.47.1.271-276.1985.
Streptococcus salivarius fructosidase (beta-D-fructan fructohydrolase, EC 3.2.1.80) was purified to homogeneity. The molecular weight of the fructosidase was estimated to be 83,000 to 85,000 by gel filtration and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pH optimum of the enzyme was 7.0, and the isoelectric point was pH 4.7. The purified enzyme preparation hydrolyzed levan, inulin, and several 2-beta-linkage-containing oligosaccharides such as sucrose and raffinose, but not melezitose, dextran, and pseudonigeran. The fructosidase was inhibited by Fe3+, Cu2+, Hg2+, and Ag+, but not by Ca2+, Co2+, Mg2+, and Zn2+, at a concentration of 10(-3) M. Mn2+ was particularly effective in stimulating activity at the same concentration. The presence of either EDTA or KCN also increased fructosidase activity by 20 to 30%. The enzyme was susceptible to sulfhydryl reagents since p-chloromercuribenzoate (10(-7) M) produced 63% inhibition of the activity. However, this inhibition was overcome in the presence of cysteine. This enzyme acts as an exofructosidase since thin-layer chromatographic analysis revealed that D-fructose was formed from levan or inulin by the action of the enzyme.
唾液链球菌果糖苷酶（β-D-果聚糖果糖水解酶，EC 3.2.1.80）被纯化至同质。通过凝胶过滤和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳估计该果糖苷酶的分子量为83,000至85,000。该酶的最适pH为7.0，等电点为pH 4.7。纯化的酶制剂可水解左聚糖、菊粉和几种含2-β-键的寡糖，如蔗糖和棉子糖，但不能水解松三糖、葡聚糖和拟黑曲霉聚糖。在10^(-3) M浓度下，该果糖苷酶受到Fe3+、Cu2+、Hg2+和Ag+的抑制，但不受Ca2+、Co2+、Mg2+和Zn2+的抑制。在相同浓度下，Mn2+对刺激活性特别有效。EDTA或KCN的存在也使果糖苷酶活性提高了20%至30%。该酶对巯基试剂敏感，因为对氯汞苯甲酸（10^(-7) M）对活性产生了63%的抑制。然而，在半胱氨酸存在下这种抑制被克服。由于薄层色谱分析表明通过该酶的作用从左聚糖或菊粉形成了D-果糖，所以这种酶起外切果糖苷酶的作用。
