title: Kinetics and thermodynamics of the thermal inactivation of polyphenol oxidase in an aqueous extract from Agaricus bisporus.
abstract: The kinetics and thermodynamics of the thermal inactivation of polyphenol oxidase (PPO) in an aqueous extract from mushroom Agaricus bisporus (J.E. Lange) Imbach was studied, using pyrocatechol as a substrate. Optimal conditions for enzymatic studies were determined to be pH 7.0 and 35-40 °C. The kinetics of PPO-catalyzed oxidation of pyrocatechol followed the Haldane model with an optimum substrate concentration of 20 mM. Thermal inactivation of PPO was examined in more detail between 50 and 73 °C and in relation to exposure time. Obtained monophasic kinetics were adequately described by a first-order model, with significant inactivation occurring with increasing temperature (less than 10% preserved activity after 6 min at 65 °C). Arrhenius plot determination and calculated thermodynamic parameters suggest that the PPO in aqueous extract from Agaricus bisporus mushroom is a structurally robust yet temperature-sensitive biocatalyst whose inactivation process is mainly entropy-driven.
authors.affiliation: UPMC-P6, CNRS, Chimie de la Matière Condensée de Paris, Collège de France, 11 place Marcelin-Berthelot, 75231 Paris cedex 05, France.
authors.forename: Hicham
authors.initials: H
authors.lastname: Gouzi
authors.forename: Christophe
authors.initials: C
authors.lastname: Depagne
authors.forename: Thibaud
authors.initials: T
authors.lastname: Coradin
mesh_terms: D000364:Agaricus / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D055162:Biocatalysis; D004156:Catechol Oxidase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D004795:Enzyme Stability; D005656:Fungal Proteins / Q000737:chemistry* / Q000302:isolation & purification; D006358:Hot Temperature; D007700:Kinetics; D013816:Thermodynamics
chemical_list: D005656:Fungal Proteins; D004156:Catechol Oxidase