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 of 6.51 mg/ml and a V 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, E₁₉₀ and E₁₉₅, conserved sites, W₁₈₃ and G₂₅₅, play important roles in Car1383 activity. This study provides a new candidate for the industrial preparation of bioactive algal oligosaccharides.