Direct analysis of donor-acceptor distance and relationship to isotope effects and the force constant for barrier compression in enzymatic H-tunneling reactions

Christopher Pudney, Linus O Johannissen, Michael J Sutcliffe, Sam Hay, Nigel S Scrutton

Research output: Contribution to journalArticlepeer-review

67 Citations (Scopus)

Abstract

The role of dynamical effects in enzyme catalysis is both complex and widely debated. Understanding how dynamics can influence the barrier to an enzyme catalyzed reaction requires the development of new methodologies and tools. In particular compressive dynamics—the focus of this study—may decrease both the height and width of a reaction barrier. By making targeted mutations in the active site of morphinone reductase we are able to alter the equilibrium of conformational states for the reactive complex in turn altering the donor−acceptor (D−A) distance for H-transfer. The sub-Å changes which we induce are monitored using novel spectroscopic and kinetic “rulers”. This new way of detecting variation in D−A distance allows us to analyze trends between D−A distance and the force constant of a compressive dynamical mode. We find that as the D−A distance decreases, the force constant for a compressive mode increases. Further, we demonstrate that—contrary to current dogma—compression may not always cause the magnitude of the primary kinetic isotope effect to decrease.
Original languageEnglish
Pages (from-to)11329-11335
JournalJournal of the American Chemical Society
Volume132
Issue number32
Early online date26 Jul 2010
DOIs
Publication statusPublished - 2010

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