A new β-agarase from marine bacterium Janthinobacterium sp. SY12

An agar-degrading bacterium, strain SY12, was identified as the genus Janthinobacterium, which is a member of the class Betaproteobacteria. A β-agarase gene agaY was cloned from SY12, and it is the first reported agarase from the Betaproteobacteria. AgaY consisted of 1,338 bp encoding 445 amino acid residues, and it was assigned to GH16 family. AgaY has an N-terminal secretary leader peptide preceding a GH16 catalytic domain and a CBM13 carbohydrate binding module. The recombinant agarase AgaY overexpressed in Escherichia coli displayed a molecular mass of 50.2 kDa and the optimum temperature and pH for the activity of the enzyme was 40°C and pH 7.0, respectively. It degraded agarose to give neoagarotetraose and neoagarobiose as the main products. Interestingly, in contrast to other agarases of GH16, the enzymatic activity of AgaY is Na+ and Ca2+ independent.