Stretched exponential decay and correlations in the catalytic activity of fluctuating single lipase molecules

Single-molecule techniques offer a unique tool for studying the dynamical behavior of individual molecules and provide the possibility to construct distributions from individual events rather than from a signal stemming from an ensemble of molecules. In biological systems, known for their complexity...

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Bibliographic Details
Main Authors: Flomenbom, O, Velonia, K, Loos, D, Masuo, S, Cotlet, M, Engelborghs, Yves, Hofkens, Johan, Rowan, AE, Nolte, RJM, Van der Auweraer, Mark, De Schryver, Frans, Klafter, J
Format: Article in Journal/Newspaper
Language:English
Published: Natl acad sciences 2005
Subjects:
single enzyme activity
two-state trajectories
candida-antarctica
conformational dynamics
enzymatic dynamics
kinetics
systems
nanocrystals
fluorescence
relaxation
f-1-atpase
Antarc*
Antarctica
Online Access:https://lirias.kuleuven.be/handle/123456789/34246
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Summary:Single-molecule techniques offer a unique tool for studying the dynamical behavior of individual molecules and provide the possibility to construct distributions from individual events rather than from a signal stemming from an ensemble of molecules. In biological systems, known for their complexity, these techniques make it possible to gain insights into the detailed spectrum of molecular conformational changes and activities. Here, we report on the direct observation of a single lipase-catalyzed reaction for extended periods of time (hours), by using confocal fluorescence microscopy. When adding a profluorescent substrate, the monitored enzymatic activity appears as a trajectory of "on-state" and "off-state" events. The waiting time probability density function of the off state and the state-correlation function fit stretched exponentials, independent of the substrate concentration in a certain range. The data analysis unravels oscillations in the logarithmic derivative of the off-state waiting time probability density function and correlations between off-state events. These findings imply that the fluctuating enzyme model, which involves a spectrum of enzymatic conformations that interconvert on the time scale of the catalytic activity, best describes the observed enzymatic activity. Based on this model, values for the coupling and reaction rates are extracted. status: published

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