Increased thermal stability of the carbonic anhydrase enzyme complex for the efficient reduction of CO₂ through cyclization and polymerization by peptide bonding

SpyCatcher and SpyTag, which form spontaneous isopeptide bonds, provide thermal and structural stability to enzymes. A Catcher/Tag system was introduced into the carbonic anhydrase (hmCA) from Hydrogenovibrio marinus to perform enzyme cyclization and polymer formation. This allows the enzyme to withstand high temperatures of 60 ℃ or higher when used as a method to reduce CO₂. A measurement of thermal stability in response to temperature change showed that the wild-type enzyme exhibited a sharp decrease in activity recovery starting at 70 ℃, but that cyclic hmCA and polymeric hmCA recovered even at 100 ℃. These results indicate that the spontaneous isopeptide bond introduced by the Catcher/Tag system provides thermal stability in enzymes. Regarding the amount of CaCO₃ synthesized by the carbonic anhydrases, the result for polymeric hmCA was more than four times higher than for wild-type hmCA. In conclusion, this study succeeded in preparing a heat-resistant carbonic anhydrase that can act at high temperatures where the wild-type enzyme is inactivated. We also show that the enzyme has the advantage of increasing CaCO₃ production. These results will provide a CO₂ capture system for coal- and natural gas-fired power plants as a way to reduce CO₂ emissions.