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°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 Fe(2+)), but inhibited or inactivated by others (Sr(2+), Ca(2+), Ni(2+), Ba(2+), Mn(2+), Cu(2+), Fe(3+), and Mg(2+)). 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.