Expression and characterization of a thermotolerant and pH-stable hyaluronate lyase from Thermasporomyces composti DSM22891

Hyaluronate lyases have received extensive attention due to their applications in medical science, drug and biochemical engineering. However, few thermotolerant and pH-stable hyaluronate lyases have been found. In this study, hyaluronate lyase TcHly8B from Thermasporomyces composti DSM22891 was expressed in Escherichia coli BL21(DE3), purified, and characterized. Phylogenetic analysis revealed that TcHly8B belonged to a new subfamily in PL8. The molecular mass of recombinant TcHly8B determined by SDS-PAGE was approximately 86 kDa. The optimal temperature of TcHly8B was 70 degrees C, which was higher than that of previously reported hyaluronate lyases. TcHly8B was very stable at temperatures from 0 to 60 degrees C. The optimal pH of TcHly8B was 6.6. It could retain more than 80% of its original enzyme activity after incubation for 12 h in the pH range of 3.0-10.6. TcHly8B degraded hyaluronic acid into unsaturated disaccharides as the end products. The amino acid sequence and structure analysis of TcHly8B demonstrated that the amino acid composition and salt bridges might contribute to the thermostability of TcHly8B. Overall, this study provides an excellent example for the discovery of thermotolerant hyaluronate lyases and can be applied to the industrialized production and basic research of hyaluronate oligosaccharides.