title: Effects of structural difference of ionic liquids on the catalysis of horseradish peroxidase.
abstract: The dependence of the catalytic properties of horseradish peroxidase on the structural changes of ionic liquids was investigated with two water-miscible ionic liquids, N-butyl-3- methypyridinium tetrafluoroborate ([BMPy][BF4]) and 1-butyl- 3-methylimidazolium methylsulfate ([BMIM][MeSO4]), each of which shares an anion (BF4 -) or a cation (BMIM+) with 1-butyl- 3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), respectively. The oxidation of guaiacol (2-methoxyphenol) with H2O2 was used as a model reaction. In order to minimize the effect of solution viscosity on the kinetic constants of the enzymatic catalysis, the enzymatic reactions for the kinetic study were performed in water-ionic liquid mixtures containing 25% (v/v) ionic liquid at maximum. Similarly to the previously reported results for [BMIM][BF4], as the concentration of [BMPy][BF4] increased, the Km value increased with a decrease in the kcat value: the Km value increased markedly from 2.8 mM in 100% water to 12.6 mM in 25% (v/v) ionic liquid, indicating that ionic liquid significantly weakens the binding affinity of guaiacol to the enzyme. On the contrary, [BMIM][MeSO4] decreased the Km value to 1.4 mM in 25% (v/v) ionic liquid. [BMIM][MeSO4] also decreased kcat more than 3- folds [from 13.8 s-1 in 100% water to 4.1 s-1 in 25% (v/v) ionic liquid]. These results indicate that the ionic liquids interact with the enzyme at the molecular level as well as at a macroscopic thermodynamic scale. Specifically, the anionic component of the ionic liquids influenced the catalysis of horseradish peroxidase in different ways.
authors: SKYBIO Team, SK Chemicals, Ulsan, Korea.
authors: Eun-Sik
authors: ES
authors: Hong
authors: Jung-Hee
authors: JH
authors: Park
authors: Ik-Keun
authors: IK
authors: Yoo
authors: Keun-Garp
authors: KG
authors: Ryu
mesh_terms: D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D006139:Guaiacol / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011726:Pyridinium Compounds / Q000737:chemistry; D014783:Viscosity
chemical_list: C525963:1-butyl-3-methylimidazolium; C419324:1-butyl-3-methylimidazolium tetrafluoroborate; C539248:1-butyl-3-methylpyridinium; D007093:Imidazoles; D052578:Ionic Liquids; D011726:Pyridinium Compounds; D006139:Guaiacol; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase