title: Biocatalytic carboxylation of phenol derivatives: kinetics and thermodynamics of the biological Kolbe-Schmitt synthesis.
abstract: Microbial decarboxylases, which catalyse the reversible regioselective ortho-carboxylation of phenolic derivatives in anaerobic detoxification pathways, have been studied for their reverse carboxylation activities on electron-rich aromatic substrates. Ortho-hydroxybenzoic acids are important building blocks in the chemical and pharmaceutical industries and are currently produced via the Kolbe-Schmitt process, which requires elevated pressures and temperatures (≥ 5 bar, ≥ 100 °C) and often shows incomplete regioselectivities. In order to resolve bottlenecks in view of preparative-scale applications, we studied the kinetic parameters for 2,6-dihydroxybenzoic acid decarboxylase from Rhizobium sp. in the carboxylation- and decarboxylation-direction using 1,2-dihydroxybenzene (catechol) as starting material. The catalytic properties (K(m), V(max)) are correlated with the overall thermodynamic equilibrium via the Haldane equation, according to a reversible random bi-uni mechanism. The model was subsequently verified by comparing experimental results with simulations. This study provides insights into the catalytic behaviour of a nonoxidative aromatic decarboxylase and reveals key limitations (e.g. substrate oxidation, CO2 pressure, enzyme deactivation, low turnover frequency) in view of the employment of this system as a 'green' alternative to the Kolbe-Schmitt processes.
authors: Institute of Technical Biocatalysis, Hamburg University of Technology, Germany.
authors: Lorenzo
authors: L
authors: Pesci
authors: Silvia M
authors: SM
authors: Glueck
authors: Pavel
authors: P
authors: Gurikov
authors: Irina
authors: I
authors: Smirnova
authors: Kurt
authors: K
authors: Faber
authors: Andreas
authors: A
authors: Liese
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D001639:Bicarbonates / Q000737:chemistry; D055162:Biocatalysis; D002262:Carboxy-Lyases / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry; D003653:Decarboxylation; D007700:Kinetics; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry*; D012231:Rhizobium / Q000201:enzymology; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D001639:Bicarbonates; D002396:Catechols; D010636:Phenols; C488807:2,6-dihydroxybenzoate decarboxylase; D002262:Carboxy-Lyases; C034221:catechol
keywords: Kolbe-Schmitt reaction; biocatalytic carboxylation; enzyme deactivation; kinetic modelling; nonoxidative carboxylation