Purification and characterization of a Na +/K + dependent alginate lyase from turban shell gut Vibrio sp. YKW-34

Abstract

An alginate lyase with high specific enzyme activity was purified from Vibrio sp. YKW-34, which was newly isolated from turban shell gut. The alginate lyase was purified by in order of ion exchange, hydrophobic and gel filtration chromatographies to homogeneity with a recovery of 7% and a fold of 25. This alginate lyase was composed of a single polypeptide chain with molecular mass of 60 kDa and isoelectric point of 5.5–5.7. The optimal pH and temperature for alginate lyase activity were pH 7.0 and 40 °C, respectively. The alginate lyase was stable over pH 7.0–10.0 and at temperature below 50 °C. The alginate lyase had substrate specificity for both poly-guluronate and poly-mannuronate units. The k cat/ K m value for alginate (heterotype) was 1.7 × 10 6 s −1 M −1. The enzyme activity was completely lost by dialysis and restored by addition of Na + or K +. The optimal activity exhibited in 0.1 M of Na + or K +. This enzyme was resistant to denaturing reagents (SDS and urea), reducing reagents (β-mercaptoethanol and DTT) and chelating reagents (EGTA and EDTA).