Characterization and Mechanism Study of a Novel PL7 Family Exolytic Alginate Lyase from Marine Bacteria Vibrio sp. W13.

Alginate lyase can degrade alginate into oligosaccharides through β-elimination for various biological, biorefinery, and agricultural purposes. Here, we report a novel PL7 family exolytic alginate lyase VwAlg7A from marine bacteria Vibrio sp. W13 and achieve the heterologous expression in E. coli BL21 (DE3). VwAlg7A is 348aa with a calculated molecular weight of 36 kDa, containing an alginate lyase 2 domain. VwAlg7A exhibits specificity towards poly-guluronate. The optimal temperature and pH of VwAlg7A are 30 °C and 7.0, respectively. The activity of VwAlg7A can be significantly inhibited by the Ni 2+ , Zn 2+ , and NaCl. The K m and V max of VwAlg7A are 36.9 mg/ml and 395.6 μM/min, respectively. The ESI and HPAEC-PAD results indicate that VwAlg7A cleaves the sugar bond in an exolytic mode. Based on the molecular docking and mutagenesis results, we further confirmed that R98, H169, and Y303 are important catalytic residues.