Characterization of a Na+-stimulated acidic hyaluronate lyase from Microbulbifer sp. ALW1 and the antioxidant activity of its hydrolysates

Hyaluronic acid (HA) is a natural polymer that can be degraded by hyaluronate lyase into oligomers with diverse biological activities. In this study, a novel hyaluronate lyase (named HCLase6) of polysaccharide lyase family 6 from Microbulbifer sp. ALW1 was cloned and characterized. Optimal temperature and pH for HCLase6 was determined to be 40 degrees C and 5.0, respectively. It displayed good stability at temperature up to 45 degrees C and in the pH range of 4.0-9.0. In addition, HCLase6 demonstrated good tolerance to detergents of Tween 20, Tween 80 and SDS, and was halophilic and halotolerant to Na+. Molecular dynamics simulations indicated that the presence of Na+ increased the flexibility of the loop region adjacent to the active pocket of HCLase6, altered the surface hydrophobicity and electrostatic potential, and strengthened the motion correlation between amino acid residues. Notably, the enzymatic products of HA oligosaccharides (O-HA) produced by HCLase6 showed significantly enhanced free radical scavenging activities and iron reducing power. They also exhibited the antioxidant activity in human keratinocytes cells after exposure to PM SRM 1648a. This study provides the knowledge of the enzymatic properties of HCLase6 and a reference for its industrial application.