Abstract
For the beneficial pharmacological properties of resveratrol, there is increasingly interest in enzymatic conversion of polydatin to resveratrol. The metagenomic technique provides an effective strategy for mining novel polydatin-hydrolysis enzymes from uncultured microorganisms. In this study, a metagenomic library of mangrove soil was constructed and a novel β-glucosidase gene MlBgl was isolated. The deduced amino acid sequences of MlBgl showed the highest identity of 64% with predicted β-glucosidase in the GenBank database. The gene was cloned and overexpressed in Escherichia coli BL21(DE3). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) assay demonstrated the purified recombinant β-glucosidase r-MlBgl with a molecular weight approximately of 71 kDa. The optimal pH and temperature of purified recombinant r-MlBgl were 7.0 and 40 °C, respectively. r-MlBgl could hydrolyze polydatin effectively. The kcat and kcat/Km values for polydatin were 989 s−1 and 1476 mM−1·s−1, respectively. These properties suggest that -r-MlBgl has potential application in the enzymatic conversion of polydatin to resveratrol for further study.
Highlights
Resveratrol (3,41,5-trihydroxystilbene), a non-flavonoid polyphenolic compound, reportedly has a wide range of pharmacological properties, including antitumor, antithrombosis, antiatherosclerosis, antioxidant, and antiinflammatory [1,2,3]
The kcat and kcat /Km values for polydatin were 989 s1 and 1476 mM1 ̈ s1, respectively. These properties suggest that -r-MlBgl has potential application in the enzymatic conversion of polydatin to resveratrol for further study
Compared with these reported β‐glucosidases, r‐MlBgl exhibited the highest productivity of resveratrol of the with these reported β-glucosidases, r-MlBgl exhibited the highest productivity of resveratrol of the β‐glucosidases from Aspergillus oryzae and Lactobacillus kimchi per unit of enzyme [12,17]. r‐MlBgl β-glucosidases from Aspergillus oryzae and Lactobacillus kimchi per unit of enzyme [12,17]. r-MlBgl exhibited higher kcat and kcat/Km values than β‐glucosidase from Lactobacillus kimchi, indicating it exhibited higher kcat and kcat /Km values than β-glucosidase from Lactobacillus kimchi, indicating it is is able to hydrolyze polydatin more effectively
Summary
Resveratrol (3,41 ,5-trihydroxystilbene), a non-flavonoid polyphenolic compound, reportedly has a wide range of pharmacological properties, including antitumor, antithrombosis, antiatherosclerosis, antioxidant, and antiinflammatory [1,2,3]. Β-Glucosidases have many applications in biological processes, such as hydrolysis of cellulose to produce ethanol [8], synthesis of alkyl glucoside and gentiooligaccharide [9], improving the flavor in food processing [10], hydrolysis of isoflavone glycosides [11], and conversion of polydatin to resveratrol [12]. The catalytic efficiency of these β-glucosidases was still not satisfied due to their low hydrolysis activity. These β-glucosidases that hydrolyse polydatin were from cultured microorganisms and little attention had been paid to β-glucosidases from unculturable microorganisms. Screening novel β-glucosidases with high conversion efficiency for polydatin from the metagenomic library is urgently demanded. The conversion of polydatin to resveratrol with metagenome-derived β-glucosidase was investigated for the first time
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