Cloning and Expression of Alginate Lyase from a Marine Bacterium, Streptomyces sp. M3

A marine bacterium was isolated from brown seaweeds for its ability to degrade alginate. Analysis of 16S ribosomal DNA sequence revealed that the strain belongs to Streptomyces like strain ALG-5 which was reported previously. New alginate lyase gene of Streptomyces sp. M3 was cloned by using PCR with the specific primers designed from homologous nucleotide sequences. The consensus sequences of N-terminal YXRSELREM and C-terminal YFKAGXYXQ were conserved in the M3 alginate lyase amino acid sequences. The homology model for the M3 alginate lyase showed a characteristic structure of β-jelly roll fold main domain like alyPG from Corynebacterium sp. ALY-1. The homogenate of the recombinant E. coli with the alginate lyase gene showed more degrading activity for polyguluronate block than polymannuronate block. The results from the multiple alignments and the homology modeling elucidated in the M3 alginate lyase can be classified into family PL-7.