Kinetic Model for the Reversible Hydration of Carbon Dioxide Catalyzed by Human Carbonic Anhydrase II

• Published in: Industrial & engineering chemistry research Vol. 49; no. 19; pp. 9095 - 9104
• Main Author: Larachi, F
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 06.10.2010
• Subjects: Applied sciences; Catalysis; Catalytic reactions; Chemical engineering; Chemistry; Exact sciences and technology; General and physical chemistry; Kinetics, Catalysis, and Reaction Engineering; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Human; Kinetic model; Catalytic reaction; Hydration; Modeling; Carbon dioxide
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie101338r

Four variants of the two-step Ping Pong mechanism for the reversible hydration of carbon dioxide to bicarbonate catalyzed by free human carbonic anhydrase II (HCA II) in solutions were derived and their goodness-of-fit to match measured initial hydration rates tested. The pseudo (i.e., no central complex) random Quad Quad Iso Ping Pong mechanism with one transitory complex was retained which implied a possible competitive intermolecular proton transfer step by the CO2/HCO3 − pair with respect to external buffer. The model suggests this role could be emphasized in product inhibition conditions at high bicarbonate/buffer concentration ratios. A 4-parameter kinetic model was derived to complement the existing single- (intra- or intermolecular) limiting-step models for HCA II catalyzed hydration of CO2 in which were accounted for altogether the enzyme isomerization and CO2/HCO3 − proton transfer via a [CO2]·[HCO3 −] coupling, the CO2/HCO3 − proton transfer via [HCO3 −]2 and [CO2]·[HCO3 −]2 couplings, and an enzyme−substrate transitory complex via [CO2]·[HCO3 −]·[Buffer] coupling. This model may prove helpful for analysis of CO2 capture reactor models subject to mixed (intra- or intermolecular) proton-transfer control, intermolecular proton transfer competition by the CO2/HCO3 − pair, and large CO2 conversions.