title: Kinetic study of the thermal inactivation of glucose oxidase in the presence of denaturant and stabilizer by means of bioelectrocatalysis method.
abstract: The thermal inactivation of glucose oxidase (GOD) in aqueous solution has been studied by the electrochemical method to follow the bioelectrocatalytic current due to the oxidation of glucose by GOD. Exponential time-dependent decrease in bioelectrocatalytic current, that is, the decrease in the enzymatic activity of GOD, was observed at given temperatures to determine the rate constant (k) of a simple inactivation process: GOD (active) → GOD (inactive). The ln[k] vs. T(-1) plots gave straight lines with all solution conditions tested, so that the resulting Arrhenius activation parameters including ΔH(‡) and ΔS(‡) can be compared with each other. In the 50 mmol/L phosphate buffer at 70°C, k was determined to be (6.6 ± 1.6)× 10(-4) s(-1), and ΔH(‡) and ΔS(‡) were calculated to be 202 ± 13 kJ mol(-1) and 282 ± 39 J K(-1) mol(-1), respectively. By addition of 3 mol/L guanidine hydrochloride, the k was increased to (4.7 ± 0.6)× 10(-3) s(-1), indicating that the denaturant accelerates the thermal inactivation. In this case, ΔH(‡) was significantly reduced. By addition of 1 g/L ε-poly-L-lysine, which may adsorb onto the GOD surface to reduce the local disorder, k was decreased to (1.8 ± 0.6)× 10(-4) s(-1). In this case, ΔS(‡) was reduced but ΔH(‡) was not decreased much. This can be used as an important indication for selection of the enzyme stabilizer in solution.
authors: Faculty of Biotechnology, Fukui Prefectural University, Eiheiji, Fukui, Japan. hajime@fpu.ac.jp
authors: Hajime
authors: H
authors: Katano
authors: Yuka
authors: Y
authors: Sugimoto
authors: Kohei
authors: K
authors: Uematsu
authors: Takao
authors: T
authors: Hibi
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology; D055162:Biocatalysis; D055664:Electrochemical Techniques / Q000379:methods*; D004789:Enzyme Activation; D004795:Enzyme Stability; D005949:Glucose Oxidase / Q000378:metabolism*; D007700:Kinetics; D011489:Protein Denaturation; D013816:Thermodynamics
chemical_list: D005949:Glucose Oxidase