Boosting the thermal stability and catalytic efficiency of <i>Sulfurihydrogenibium yellowstonense</i> carbonic anhydrase through proline substitutions

The urgent need to address global warming necessitates the development of advanced technologies for carbon capture and storage (CCS). Although carbon dioxide absorption into alkanolamines or carbonate solutions is among the most common CCS processes, these approaches harbor some limitations. Carbonic anhydrase enzymes can significantly increase the efficacy of CO₂ absorption into capture solvent solutions. Carbonic anhydrase from Sulfurihydrogenibium yellowstonense (SspCA) is a well-known enzyme with favorable properties for CO₂ absorption into capture solutions. Here, using computational tools, strategic proline substitutions were designed to enhance the thermal stability of SspCA. Compared to the wild type, the engineered mutants, E145P and N153P, showed an increase of 1.6-4.3 °C in the melting temperature. After 14 h at 80 °C, the wild type retained only 6% ± 1% of its initial activity, while N153P and E145P retained 33% ± 3% and 44% ± 1%, respectively. The E145P and N153P mutants in aqueous potassium carbonate medium at 60 °C outperformed the wild type in retention of CO₂ hydration activity. In addition, an increase in the catalytic efficiency of the E145P mutant, along with a decrease in its K_m value, indicated that proline substitution facilitates substrate binding. Molecular dynamics simulations exhibited the proline-induced structural changes, particularly reduced terminal fluctuations. Structural studies unveiled the formation of a new salt bridge connecting the C- and N-terminal regions of carbonic anhydrase, contributing to reduced fluctuations and enhanced stability. This study underscores the success of introducing proline substitutions in fortifying carbonic anhydrase stability and catalytic efficacy, which is vital for enzymatic carbon capture and storage technologies.