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The role of reaction energy and hydrogen bonding in the reaction path of enzymatic proton transfers
Author(s) -
Barroso Monica,
Arnaut Luis G.,
Formosinho Sebastião J.
Publication year - 2009
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1463
Subject(s) - chemistry , intramolecular force , enzyme catalysis , catalysis , proton , proton coupled electron transfer , transition state , photochemistry , reaction rate , computational chemistry , stereochemistry , electron transfer , organic chemistry , physics , quantum mechanics
The reaction path of the Interacting‐State Model is used with the Transition‐State Theory and the semiclassical correction for tunneling (ISM/scTST) to calculate proton transfer rates in rate‐determining CH bond breaking by enzymes such as mandelate racemase, triose‐phosphate isomerase, methylamine dehydrogenase (MADH), and aromatic amine dehydrogenase (AADH), as well as of the analogous uncatalyzed proton transfers in aqueous solution. This method employs the reaction energy, the bond distances in reactants and products, and properties of the reactive bonds to calculate the proton transfer rates. The comparison between the molecular factors that control reactivity in solution and in the enzymes reveals the following salient features of enzyme catalysis: (1) the change from a bimolecular reaction in solution to an intramolecular reaction with negligible activation entropy in the enzyme; (2) energetic stabilization of the intermediates; and (3) extreme tunneling corrections when hydrogen bonding to a carbon atom is present in the reaction path. Copyright © 2008 John Wiley & Sons, Ltd.