title: A novel pathway to enzyme deactivation: the cutinase model.
abstract: Cutinase in aqueous solution at pH 4.5 deactivates following a parallel pathway. At 53 degrees C, 88% of the cutinase molecules are in the unfolded conformation, which can aggregate with a reaction order of 3 if the protein concentration is high (>/=12 microM). The aggregates show a sixfold increase in size as determined by dynamic light scattering. This aggregation process is the first phase observed during a deactivation experiment; however, after significant cutinase depletion and maturation of the aggregates, a first-order step starts to dominate and a second phase independent of the protein concentration is observed. Kinetic partitioning between aggregation and first-order irreversible changes of the unfolded conformation can occur during enzyme deactivation when the equilibrium between the native and the unfolded conformation is shifted and kept toward the unfolded conformation.
authors.affiliation: Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Av. Rovisco Pais, Lisboa, Portugal.
authors.forename: R P
authors.initials: RP
authors.lastname: Baptista
authors.forename: L Y
authors.initials: LY
authors.lastname: Chen
authors.forename: A
authors.initials: A
authors.lastname: Paixão
authors.forename: J M S
authors.initials: JM
authors.lastname: Cabral
authors.forename: E P
authors.initials: EP
authors.lastname: Melo
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D003198:Computer Simulation; D003461:Crystallography / Q000379:methods*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D004795:Enzyme Stability; D046911:Macromolecular Substances; D008956:Models, Chemical; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D004791:Enzyme Inhibitors; D046911:Macromolecular Substances; D012996:Solutions; D014867:Water; D002265:Carboxylic Ester Hydrolases; C019952:cutinase