Characterization of Structure and Properties of α-L-Rhamnosidase from Aspergillus aculeatus
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Abstract:
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.
