title: Effect of detergents, trypsin and unsaturated fatty acids on latent loquat fruit polyphenol oxidase: basis for the enzyme's activity regulation.
abstract: The effects of detergents, trypsin and fatty acids on structural and functional properties of a pure loquat fruit latent polyphenol oxidase have been studied in relation to its regulation. Anionic detergents activated PPO at pH 6.0 below critical micelle concentration (cmc), but inhibited at pH 4.5 well above cmc. This behavior is due to a detergent-induced pH profile alkaline shift, accompanied by changes of intrinsic fluorescence of the protein. Gel filtration experiments demonstrate the formation of PPO-SDS mixed micelles. Partial PPO proteolysis suggest that latent PPO losses an SDS micelle-interacting region but conserves an SDS monomer-interacting site. Unsaturated fatty acids inhibit PPO at pH 4.5, the strongest being linolenic acid while the weakest was gamma-linolenic acid for both, the native and the trypsin-treated PPO. Down-regulation of PPO activity by anionic amphiphiles is discussed based on both, the pH profile shift induced upon anionic amphiphile binding and the PPO interaction with negatively charged membranes.
authors.affiliation: Grupo de Proteómica y Genómica Funcional de Plantas, Departamento de Agroquímica y Bioquímica, Facultad de Ciencias, Universidad de Alicante, Campus de San Vicente del Raspeig, Apdo, 99, E-03080 Alicante, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Sellés-Marchart
authors.forename: Juan
authors.initials: J
authors.lastname: Casado-Vela
authors.forename: Roque
authors.initials: R
authors.lastname: Bru-Martínez
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry*; D003902:Detergents / Q000737:chemistry*; D004789:Enzyme Activation; D031983:Eriobotrya / Q000201:enzymology*; D005231:Fatty Acids, Unsaturated / Q000502:physiology*; D005638:Fruit / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D010936:Plant Extracts / Q000737:chemistry*; D014357:Trypsin / Q000737:chemistry*
chemical_list: D003902:Detergents; D005231:Fatty Acids, Unsaturated; D010936:Plant Extracts; D004156:Catechol Oxidase; D014357:Trypsin