Cloning and Characterization of an Alginate Lyase from Marine Vibrio. sp. QD-5

The string of bacteria, Vibrio. sp. QD-5 utilizing alginate, was separated from rotten kelp. The results of genome sequencing showed that the strain QD-5 contained four alginate lyase genes.One of the alginate genes Aly-IV was cloned and linked to the plasmid pET-22b (+). The heterologous expressed alginate lyase aly-IVwas characterized,which possessed the theoretical molecular mass of 62 kDa, and theoretical isoelectric point (pI) of 5.12. The enzyme aly-IV was purified and the activity reached 1256.78 U/mg, with optimal temperature of 35 oC and pH value of 8.9. Nurtured in the temperature below 25 oC for 30 minutes, the activity was almost stable. The result also suggested that the activity of enzyme was strongly affected by NaCl whose optimal concentration was 15 mM in a lab environment The TLC and ESI-TOF-MS analysis suggested that the enzyme aly-IV could degrade sodium alginate and polyG in endo-lytic type, producing monomer, dimer and trimmer. So, aly-IV can also be widely applied to make large scale preparation of alginate oligosaccharides with low degree of polymerization (DP). Keywards: alginate lyase; Vibrio sp.QD-5; alginate