title: Ever-fluctuating single enzyme molecules: Michaelis-Menten equation revisited.
abstract: Enzymes are biological catalysts vital to life processes and have attracted century-long investigation. The classic Michaelis-Menten mechanism provides a highly satisfactory description of catalytic activities for large ensembles of enzyme molecules. Here we tested the Michaelis-Menten equation at the single-molecule level. We monitored long time traces of enzymatic turnovers for individual beta-galactosidase molecules by detecting one fluorescent product at a time. A molecular memory phenomenon arises at high substrate concentrations, characterized by clusters of turnover events separated by periods of low activity. Such memory lasts for decades of timescales ranging from milliseconds to seconds owing to the presence of interconverting conformers with broadly distributed lifetimes. We proved that the Michaelis-Menten equation still holds even for a fluctuating single enzyme, but bears a different microscopic interpretation.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: English
authors.forename: Wei
authors.initials: W
authors.lastname: Min
authors.forename: Antoine M
authors.initials: AM
authors.lastname: van Oijen
authors.forename: Kang Taek
authors.initials: KT
authors.lastname: Lee
authors.forename: Guobin
authors.initials: G
authors.lastname: Luo
authors.forename: Hongye
authors.initials: H
authors.lastname: Sun
authors.forename: Binny J
authors.initials: BJ
authors.lastname: Cherayil
authors.forename: S C
authors.initials: SC
authors.lastname: Kou
authors.forename: X Sunney
authors.initials: XS
authors.lastname: Xie
mesh_terms: D002384:Catalysis; D005697:Galactosides / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008968:Molecular Conformation; D010078:Oxazines / Q000737:chemistry / Q000378:metabolism; D001616:beta-Galactosidase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D005697:Galactosides; D010078:Oxazines; C056561:resorufin galactopyranoside; D001616:beta-Galactosidase