Characterization of a Thermostable and Surfactant-Tolerant Chondroitinase B from a Marine Bacterium Microbulbifer sp. ALW1

Chondroitinase plays an important role in structural and functional studies of chondroitin sulfate (CS). In this study, a new member of chondroitinase B of PL6 family, namely ChSase B6, was cloned from marine bacterium Microbulbifer sp. ALW1 and subjected to enzymatic and structural characterization. The recombinant ChSase B6 showed optimum activity at 40 degrees C and pH 8.0, with enzyme kinetic parameters of K-m and V-max against chondroitin sulfate B (CSB) to be 7.85 mu g/mL and 1.21 U/mg, respectively. ChSase B6 demonstrated thermostability under 60 degrees C for 2 h with about 50% residual activity and good pH stability under 4.0-10.0 for 1 h with above 60% residual activity. In addition, ChSase B6 displayed excellent stability against the surfactants including Tween-20, Tween-80, Trion X-100, and CTAB. The degradation products of ChSase B6-treated CSB exhibited improved antioxidant ability as a hydroxyl radical scavenger. Structural analysis and site-directed mutagenesis suggested that the conserved residues Lys248 and Arg269 were important for the activity of ChSase B6. Characterization, structure, and molecular dynamics simulation of ChSase B6 provided a guide for further tailoring for its industrial application for chondroitin sulfate bioresource development.

Automated summary

In this study, a new member of chondroitinase B, ChSase B6, was cloned and characterized. The recombinant enzyme showed optimal activity at 40°C and pH 8.0, and demonstrated thermostability and pH stability. ChSase B6 also displayed stability against surfactants and improved the antioxidant ability of chondroitin sulfate. Structural analysis and mutagenesis suggested the importance of specific residues for the activity of ChSase B6. The characterization and structure of ChSase B6 provided guidance for its industrial application in chondroitin sulfate bioresource development.