Biocatalytic kinetics of the reaction between CO2 and tertiary amine using carbonic anhydrase

Abstract

Carbonic anhydrase (CA) is a high-efficiency biocatalyst that significantly improves the absorption of CO₂ by tertiary amine. This work aims to investigate kinetics behaviors from the perspective of enzymatic reaction mechanism. The influences of the CA concentration, type of tertiary amines, pH, and temperature on the reaction rate between CO₂ and tertiary amine (ν) and catalytic activity of CA (φ) were first investigated in a stopped-flow device. Adding 50 g∙m⁻³ CA enhanced ν in tertiary amine solutions by a factor ranging from 22 to 42 at 298 K and pH=9.5, demonstrating its excellent catalytic performance. The ν increased with increasing CA concentration, pH, temperature, and tertiary amine's pKa. φ increased with the increase of CA concentration, as well as the decrease of temperature, pH, and tertiary amine's pKa. Proteomics analysis further revealed that conformational changes of the CA's secondary structure induced by high pH and temperature altered the expressions of the local active-site region and deactivated CA, ultimately leading to a decrease in φ. Additionally, the CA-catalysis kinetics equation accorded with the Michaelis-Menten model, with catalytic second-order rate constants on the magnitude of 10⁷. Overall, this work provides a guideline for its industrial application in the CO₂ capture process.