中文摘要：

目的：研究大蒜（Allium sativum L.）果聚糖水解酶（FEH）的酶学特征。方法：采用硫酸铵分级沉淀确定FEH所在的沉淀组分,采用薄板层析和离子色谱法研究酶解产物,通过3,5-二硝基水杨酸（DNS）法测定还原糖的变化量计算酶活力,进而研究FEH的酶切位点,研究温度、pH值、离子强度、底物质量浓度对FEH活力的影响。结果：大蒜FEH存在于0～20%硫酸铵饱和度组分,根据酶解产物判断该酶属于外切酶,最适反应温度为45℃,最适反应pH值为5.5,最适离子强度为1.5mol/L氯化钠,最适反应质量浓度为4mg/mL。结论：存在于大蒜中的果聚糖外切酶会影响大蒜加工产品的质量和保鲜大蒜贮藏的糖代谢。

英文摘要：

Fructans occupy more than 75% of the dry weight of garlic（Allium sativum L.）.Understanding of the enzymologic characteristics of garlic fructan exohydrolase（FEH） provides the theoretical basis on inhibition of garlic germination and mass production of high quality garlic fructans.In this experiment,localization of FEH was done by ammonium sulfate precipitation,its enzymatic degradation products were studied by TLC and ion chromatography,enzyme activity was determined by calculating the variance of reducing sugar via DNS assay.Further study of the locus of action of FEH and the effects of temperature,pH level,ionic strength,and substrate concentration on FEH activity was also included.The results showed that FEH was present in the fraction of 0-20% saturated ammonium sulphate.Through the analysis of enzymatic degradations,FEH was confirmed as an excision enzyme.The optimal reaction temperature,pH,ionic strength and substrate concentration were 45 ℃,pH 5.5,1.5 mol/L and 4 mg/mL,respectively.These investigations demonstrated that the exohydrolase in garlic could impact the quality of garlic processed products and polysaccharide metabolization in the fresh garlic during its storage.