Purification and characterization of the extracellular alginate lyase from Streptomyces sp. MET 0515

We isolated a new extracellular alginate lyase-producing microorganism, which displayed alginate-depolymerizing activity in plate assays, from coastal soils in Wando, Jeollanam-do, Korea. This alginate-depolymerizing bacterium belonged to the genus Streptomyces and it was named Streptomyces sp. MET 0515. An extracellular alginate lyase (ALY1) secreted by Streptomyces sp. MET 0515, was purified to homogeneity by a combination of acetone precipitation, anion-exchange chromatography (Q-Sepharose and DEAE-Sepharose) and Sephacryl S-200 HR gel filtration chromatography. Its molecular mass was 26 kDa as determined by SDS-PAGE analysis. The enzyme had an optimal temperature of 70℃ for its activity, and was most active at pH 7.5. The thermal and pH stability were 0-50℃, and pH 6.0-9.0, respectively. The enzyme activity was stimulated by 1mM Mn²?, and inhibited by 1mM Fe³?, 1mM EDTA and 1mM Zn²?. Preliminary analysis of substrate specificity showed that this alginate lyase had activity on both poly-alpha 1,4-L-guluronate and poly-beta 1,4-D-mannuronate in the alginate molecule.