Stabilization of Bovine carbonic anhydrase II through rational site-specific immobilization

Abstract

Carbonic anhydrase (CA) is a prominent biocatalyst used for the enzymatic CO2 capture process. For industrial applications, the immobilization of enzyme on a matrix support is a useful technique for stabilizing the enzyme and improving its reusability. Although there have been several trials for immobilization of CA, there is no systematic approach to investigate which site-specific immobilization is more effective for stabilization of CA. In this study, we investigated the effect of the immobilization position on the stability of CA using α-type Bovine CA (bCAII). Six candidate residues (K9, K36, T85, D151, E233, or N252) were selected and each Cys mutant was site-specifically immobilized on the magnetic beads. The thermal and long-term stabilities were compared. Interestingly, the immobilized K9C and K36C, in which the immobilized sites are located close to the N-terminus of bCAII, showed 4.0- and 9.8-fold enhanced thermostability, respectively, at 58 °C. They also maintained 60.6% and 55.5% of activity, respectively, at 45 °C after 20 days, when the wild-type bCAII (free and randomly immobilized) completely lost its activity. These results indicated that the site-specific immobilization of the flexible residues on the N-terminal region could be an effective strategy for the stabilization of bCAII, which would be useful guidelines for the immobilization of other CAs in a site-specific manner.