塔宾曲霉固态发酵产物中α-L-鼠李糖苷酶的分离纯化及酶学性质分析

Purification and characterization of an α- L- rhamnosidase from the solid- state fermentation product of Aspergillus tubingensis

α-L-鼠李糖苷酶是一种在食品、药品中有重要用途的糖苷酶,但其结构与功能关系尚不明确,限制了优良酶制剂的设计。本文通过硫酸铵分级沉淀、疏水层析和亲和层析从塔宾曲霉固态发酵柚皮产物中分离纯化得到了一种α-L-鼠李糖苷酶,纯化倍数和比活力分别为34和21105 IU/mg,SDS-PAGE测得该酶的分子质量为120 ku;纯化得到的α-L-鼠李糖苷酶最适反应p H为4.0,最适反应温度为50℃,p H稳定性和热稳定性好;Fe^(2+)对酶活有促进作用,Mn^(2+)、Ca^(2+)、Cd^(2+)对酶有抑制作用;该酶可水解柚皮苷,但对芸香苷和对硝基苯酚鼠李糖的转化率较低,不水解杨梅苷和柴胡皂苷C。以上结果表明纯化得到的α-L-鼠李糖苷酶在金属离子影响特性、底物特异性方面具有新颖性,丰富了α-L-鼠李糖苷酶的结构与功能关系研究素材。

α-L-rhamnosidase is a kind of glycosidase that is of great significance in food and pharmaceutical industry, however, the function -structure relationships is unclear, which hinders the design and production of excellent α-L- rhamnosidase for industrial use.In this study,α-L- rhamnosidase was separated and purified by ammonium sulfate precipitation,hydrophobic interaction chromatography and affinity chromatography from a solid -state fermentation broth of Aspergillus tubingensis on the matrix of pomelo peel powder.The purification factor and specific activity were 34 and 21105 IU/mg, respectively.SDS - PAGE revealed an apparent molecular weight of 120 ku.The pH and temperature optima were 4.0 and 50 ℃, respectively.The enzyme had good thermal and pH stability.Divalent cations Fe2＋ stimulated the α-L- rhamnosidase activity,whereas Mn2 ＋ , Ca2＋ and Cd2 ＋ inhibited the activity.This enzyme showed the capacity to hydrolyze naringin, but showed little capacity to hydrolyze rutin and p -nitrophenyl-α-L-rhamnopyranoside and couldn＇t hydrolyze myricetrin and saikosaponin C.These results indicated the enzyme had the metal ionic affecting property and substrates specificity different from those of previous studies, providing a new type of enzyme for investigating function - structure relationship of α-L-rhamnosidase.