Cloning and sequencing of agaA, a unique agarase 0107 gene from a marine bacterium, Vibrio sp. strain JT0107

An agarase gene (agaA) was cloned from genomic DNA of Vibrio sp. strain JT0107. An open reading frame of 2,985 nucleotides gave a primary translation product composed of the mature protein, agarase 0107 (975 amino acid residues, with a molecular weight of 105,271) and a signal peptide of 20 amino acid residues at the N terminus. Comparison of the deduced amino acid sequence of agarase 0107 with those of Streptomyces coelicolor and Pseudomonas atlantica suggests that these enzymes share two regions in common. The AgaA protein which was expressed in Escherichia coli had the agarase activity. Agarase 0107 hydrolyzes not only agarose but also neoagarotetraose [O-3,6-anhydro-alpha-L-galactopyranosyl (1-->3)-O-beta-D-galactopyranosyl(1-->4)-O-3,6-anhydro-alpha-L-galact opy ranosyl (1-->3)-D-galactose] to yield neoagarobiose [O-3,6-anhydro-alpha-L-galactopyranosyl(1-->3)-D-galactose]. This is a quite unique characteristic for a beta-agarase.