title: Single-molecule enzymatic conformational dynamics: spilling out the product molecules.
abstract: Product releasing is an essential step of an enzymatic reaction, and a mechanistic understanding primarily depends on the active-site conformational changes and molecular interactions that are involved in this step of the enzymatic reaction. Here we report our work on the enzymatic product releasing dynamics and mechanism of an enzyme, horseradish peroxidase (HRP), using combined single-molecule time-resolved fluorescence intensity, anisotropy, and lifetime measurements. Our results have shown a wide distribution of the multiple conformational states involved in active-site interacting with the product molecules during the product releasing. We have identified that there is a significant pathway in which the product molecules are spilled out from the enzymatic active site, driven by a squeezing effect from a tight active-site conformational state, although the conventional pathway of releasing a product molecule from an open active-site conformational state is still a primary pathway. Our study provides new insight into the enzymatic reaction dynamics and mechanism, and the information is uniquely obtainable from our combined time-resolved single-molecule spectroscopic measurements and analyses.
authors.affiliation: Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.
authors.forename: Desheng
authors.initials: D
authors.lastname: Zheng
authors.forename: H Peter
authors.initials: HP
authors.lastname: Lu
mesh_terms: D000838:Anions / Q000737:chemistry; D016880:Anisotropy; D002384:Catalysis; D020134:Catalytic Domain; D005453:Fluorescence; D006735:Horseradish Peroxidase / Q000737:chemistry*; D008968:Molecular Conformation; D010078:Oxazines / Q000737:chemistry; D010084:Oxidation-Reduction; D012399:Rotation
chemical_list: D000838:Anions; D010078:Oxazines; C470430:Amplex Red; C014180:resorufin; D006735:Horseradish Peroxidase