Characterization of a New Cold-Adapted and Salt-Activated Polysaccharide Lyase Family 7 Alginate Lyase from Pseudoalteromonas sp SM0524

Marine bacterial alginate lyases play a role in marine alginate degradation and carbon cycling. Although a large number of alginate lyases have been characterized, reports on alginate lyases with special characteristics are still rather less. Here, a gene alyPM encoding an alginate lyase of polysaccharide lyase family 7 (PL7) was cloned from marine Pseudoalteromonas sp. SM0524 and expressed in Escherichia coil. AIyPM shows 41% sequence identity to characterized alginate lyases, indicating that AIyPM is a new PL7 enzyme. The optimal pH for AIyPM activity was 8.5. AIyPM showed the highest activity at 30 degrees C and remained 19% of the highest activity at 5 degrees C. AIyPM was unstable at temperatures above 30 degrees C and had a low T-m of 37 degrees C. These data indicate that AIyPM is a cold-adapted enzyme. Moreover, AIyPM is a salt-activated enzyme. AIyPM activity in 0.5-1.2 M NaCI was sixfolds higher than that in 0 M NaCI, probably caused by a significant increase in substrate affinity, because the Km of AIyPM in 0.5 M NaCI decreased more than 20-folds than that in 0 M NaCI. AIyPM preferably degraded polymannuronate and mainly released dimers and trimers. These data indicate that AIyPM is a new PL7 endo-alginate lyase with special characteristics.