[Purification and characterization of alginate lyase from marine bacterium Vibrio sp. QY101]

Extracellular alginate lyase secreted by Vibrio sp. QY101, which was isolated from brown algae, was purified to homogeneity by a combination of ammonium sulfate precipitation, DEAE-Sepharose Fast Flow anion-exchange chromatography and Superdex 75 gel filtration chromatography. Its molecular mass was 39 kD as determined by SDS-PAGE analysis. The enzyme had an optimal temperature of 30 degrees for its activity, and was most active at pH 7.5. The thermal and pH stability were 0-30 degrees, and pH 6.5-8.5, respectively. The enzyme activity was stimulated by 0.5 mol/L NaCl, 1.0 mmol/L Ca(2+) or 5.0 mmol/L (Mn(2+), and inhibited by 5.0 mmol/L Ni(2+), 1.0 mmol/L Fe2+) or 1.0 mmol/L EDTA. Preliminary analysis on substrate specificity showed that this alginate lyase had activity on both poly-alpha 1,4-L-guluronate and poly-beta1,4-D-mannuronate substrates.