title: Kinetics of Horseradish Peroxidase-Catalyzed Nitration of Phenol in a Biphasic System.
abstract: The use of peroxidase in the nitration of phenols is gaining interest as compared with traditional chemical reactions. We investigated the kinetic characteristics of phenol nitration catalyzed by horseradish peroxidase (HRP) in an aqueous-organic biphasic system usingn-butanol as the organic solvent and NO2-and H2O2as substrates. The reaction rate was mainly controlled by the reaction kinetics in the aqueous phase when appropriate agitation was used to enhance mass transfer in the biphasic system. The initial velocity of the reaction increased with increasing HRP concentration. Additionally, an increase in the substrate concentrations of phenol (0-2 mM in organic phase) or H2O2(0-0.1 mM in aqueous phase) enhanced the nitration efficiency catalyzed by HRP. In contrast, high concentrations of organic solvent decreased the kinetic parameterVmax/Km. No inhibition of enzyme activity was observed when the concentrations of phenol and H2O2were at or below 10 mM and 0.1 mM, respectively. On the basis of the peroxidase catalytic mechanism, a double-substrate ping-pong kinetic model was established. The kinetic parameters wereKmH2O2= 1.09 mM,KmPhOH= 9.45 mM, andVmax= 0.196 mM/min. The proposed model was well fit to the data obtained from additional independent experiments under the suggested optimal synthesis conditions. The kinetic model developed in this paper lays a foundation for further comprehensive study of enzymatic nitration kinetics.
authors: School of Life Science, Beijing Institute of Technology, Beijing 100081, P.R. China.
authors: Mingming
authors: M
authors: Kong
authors: School of Life Science, Beijing Institute of Technology, Beijing 100081, P.R. China.
authors: Yang
authors: Y
authors: Zhang
authors: School of Life Science, Beijing Institute of Technology, Beijing 100081, P.R. China.
authors: Qida
authors: Q
authors: Li
authors: School of Life Science, Beijing Institute of Technology, Beijing 100081, P.R. China.
authors: Runan
authors: R
authors: Dong
authors: School of Life Science, Beijing Institute of Technology, Beijing 100081, P.R. China.
authors: Haijun
authors: H
authors: Gao
mesh_terms: D020001:1-Butanol / Q000378:metabolism; D055162:Biocatalysis; D006735:Horseradish Peroxidase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D009566:Nitrates / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D009930:Organic Chemicals / Q000378:metabolism; D019800:Phenol / Q000737:chemistry* / Q000378:metabolism; D011930:Reaction Time / Q000502:physiology; D012997:Solvents
chemical_list: D009566:Nitrates; D009930:Organic Chemicals; D012997:Solvents; D009569:Nitric Oxide; D019800:Phenol; D020001:1-Butanol; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase
keywords: Horseradish peroxidase; kinetics; modeling; nitration; organic-aqueous biphasic system