Biochemical Characterization of a Carrageenase, Car1383, Derived From Associated Bacteria of Antarctic Macroalgae

A carrageenase gene, car1383, was obtained from the metagenome of Antarctic macroalgae-associated bacteria. The amino acid sequence of its product showed up to 33% similarity with other carrageenases and contained a GH16-family motif. The recombinant Car1383 was heterologously expressed in Eschericia coli and exhibited maximal activity at 50 degrees C and pH 6.0, with a K-m of 6.51 mg/ml and a V-max of 55.77 U/mg. Its activity was enhanced by some cations (Na+, K+, and Fe2+), but inhibited or inactivated by others (Sr2+, Ca2+, Ni2+, Ba2+, Mn2+, Cu2+, Fe3+, and Mg2+). Car1383 degraded carrageenan into neocarrabiose and neocarratetraose. Site-directed mutagenesis indicated that putative active sites, E-190 and E-195, conserved sites, W-183 and G(255), play important roles in Car1383 activity. This study provides a new candidate for the industrial preparation of bioactive algal oligosaccharides.