α-L-鼠李糖苷酶是一种具有重要应用价值的诱导酶。目前，α-L-鼠李糖苷酶的结构与功能关系尚不明确。本文以柚皮苷为诱导物培养棘孢曲霉产α-L-鼠李糖苷酶，研究该酶的结构及酶学性质特征。经质谱分析该α-L-鼠李糖苷酶属于棘孢曲霉α-L-鼠李糖苷酶A。三维结构模拟发现该α-L-鼠李糖苷酶具有N端β-折叠结构域、C端β-折叠结构域、clan-L (alpha/alpha)(6)-桶状催化结构域以及具有Asp等九个完全保守氨基酸残基，说明该酶属于糖苷酶78家族成员。分子对接发现该酶通过酸碱催化的机制水解柚皮苷。该酶的最适温度50 ℃，最适pH 4.0，1 mM与10 mM的Ag+、Fe2+及Fe3+对该酶有较强的抑制作用；该酶可以水解柚皮苷、橙皮苷和杨梅苷，其水解柚皮苷的动力学符合典型的米氏方程，Km值为0.23 mM，Vmax为565.1 U/mg。以上结果丰富了α-L-鼠李糖苷酶的结构与功能关系的研究理论，为开发性质优良的α-L-鼠李糖苷酶提供了信息参考。

α-L-Rhamnosidase is an inducible enzyme with important applications. Currently, the structure-function relationship of α-L-Rhamnosidase is not clear. Aspergillus aculeatus was cultivated using naringin as the α-L-rhamnosidase inducer, and the structural characteristics and enzymatic properties of this enzyme were studied. Mass spectrometry analysis revealed that this α-L-rhamnosidase was the α-L-rhamnosidase A (RhA) variant from A. aculeatus. The simulations of three-dimensional structure of the enzyme revealed that α-L-rhamnosidase had one N-terminal β-sheet domain, one C-terminal β-sheet domain, a clan-L (alpha/alpha)-barrel structure as a catalytic structure domain and nine fully conserved amino acid residues (e.g., Asp), indicating that this enzyme belongs to the glycoside hydrolase (GH78) family. The molecular docking results showed that this enzyme could hydrolyze naringin through an acid/base-catalyzed hydrolysis pathway. The optimal temperature and pH for the enzymatic reaction were 50 ℃ and 4.0, respectively, while 0.1 mM and 10 mM Ag+, Fe2+ and Fe3+ had strong inhibitory effects on the enzyme. Moreover, α-L-rhamnosidase investigated in this study was able to hydrolyze naringin, hesperidin and myricitrin. The kinetics of naringin hydrolysis followed the typical Michaelis-Menten equation, with a Km value of 0.23 mM and a Vmax of 565.1 U/mg. These results contribute to the structure-function relationships of α-L-rhamnosidase, and provide useful information for the production of α-L- rhamnosidase with excellent characteristics.

国家自然科学基金资助项目（31371751）；集美大学科研创新团队基金( 2010A006)