Cloning, sequence analysis, and expression of gene alyPI encoding an alginate lyase from marine bacterium Pseudoalteromonas sp CY24

The alginate lyase encoding gene (alyPI) of marine bacterium Pseudoalteromonas sp. CY24 was cloned using a battery of PCR techniques. Gene alyPI was composed of a 1575 bp open reading frame encoding a protein of 57.4 kDa containing 524 amino acid residues with a signal peptide of 23 amino acids. The AlyPI protein was expressed in Escherichia coli with a His-tag sequence fused at the C-terminal end and purified to electrophoretic homogeneity using Ni-sepharose affinity chromatography. AlyPI was most active at 40 degrees C and pH 7.0 in the presencce of 0.1 mol/L NaCl and stable over a broad range of pH, 6.0-10.6. The presence of Na+, K+, Mn2+, Ca2+, and Fe3+, can enhance the enzyme activity. The alginate lyase consensus region YFKAGXYXQ, regarded as a striking feature at the C termini of several alginate lyase of similar to 30 kDa, was found in AlyPI, which belongs to the similar to 60 kDa group. Another nine amino acid consensus region, YXRSELREM, only found in G-specific alginate lyases previously existed in AlyPI, which could degrade sodium alginate, M blocks, and G blocks and appeared to be a broad substrate-specific alginate lyase.