Enzymatic Properties of Laminarinase Lam128A from Microbulbifer sp. ALW1 and Antioxidant Activity of Its Enzymatic Hydrolysates
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Abstract:
The enzymatic properties of laminarinase Lam128A derived from Microbulbifer sp. ALW1 and antioxidant activity of its enzymatic hydrolysates were investigated. Recombinant laminarinase (rLam128A) with a molecular mass of 70 ku was heterologously expressed in Pichia pastoris. The optimal reaction temperature and pH were 45°C and 5.5, respectively. The enzyme was stable at temperatures below 45 °C, and the residual enzyme activity did not drop below 60% following treatment at pH 3.0, 5.0, and 11.0 for 96 h. The reducing reagent dithiothreitol promoted laminarinase activity. rLam128A showed good stability in the presence of the chelating agent ethylenediaminetetraacetic acid as well as certain stability in the presence of the detergents Tween 20, Tween 80, and denaturant urea. Following laminarin hydrolysis by rLam128A, the IC50 values of the hydrolysates against DPPH, ABTS, and OH free radicals were 7.12, 1.01, and 2.40 mg/mL, respectively. These results indicate that the enzymatic hydrolysates exhibited more significant antioxidant activity than the unhydrolyzed laminarin. The above enzymatic properties of laminarinase Lam128A from Microbulbifer sp. ALW1 provide a theoretical basis for its application in the development and utilization of biological resources of laminarin.
