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Published April 9, 2009 | public
Journal Article

A Kinetic Model for the Enzymatic Action of Cellulase


We develop a mechanochemical model for the dynamics of cellulase, a two-domain enzyme connected by a peptide linker, as it extracts and hydrolyzes a cellulose polymer from a crystalline substrate. We consider two random walkers, representing the catalytic domain (CD) and the carbohydrate binding module (CBM), whose rates for stepping are biased by the coupling through the linker and the energy required to lift the cellulose polymer from the crystalline surface. Our results show that the linker length and stiffness play a critical role in the cooperative action of the CD and CBM domains and that, for a given linker length, the steady-state hydrolysis shows a maximum at some intermediate linker stiffness. The maximum hydrolysis rate corresponds to a transition of the linker from a compressed to an extended conformation, where the system exhibits maximum fluctuation, as measured by the variance of the separation distance between the two domains and the dispersion around the mean hydrolysis speed. In the range of experimentally known values of the parameters of our model, improving the intrinsic hydrolytic activity of the CD leads to a proportional increase in the overall hydrolysis rate.

Additional Information

© 2009 American Chemical Society. Received: December 3, 2008; Revised Manuscript Received: January 30, 2009. Publication Date (Web): March 17, 2009. We thank Bradley Olsen, Frances Arnold, and Pete Heinzelman for helpful discussions. C.L.T. is thankful for financial support from an NIH training grant. D.E.M. acknowledges financial support from the Robert A. Welch Foundation (Grant F-1514) and the National Science Foundation (Grant CHE 0347862).

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