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@ARTICLE{Kulkarni:836814,
author = {Kulkarni, Yashraj S. and Liao, Qinghua and Petrovic, Dusan
and Krüger, Dennis M. and Strodel, Birgit and Amyes, Tina
L. and Richard, John P. and Kamerlin, Shina C. L.},
title = {{E}nzyme {A}rchitecture: {M}odeling the {O}peration of a
{H}ydrophobic {C}lamp in {C}atalysis by {T}riosephosphate
{I}somerase},
journal = {Journal of the American Chemical Society},
volume = {139},
number = {30},
issn = {0002-7863},
address = {Washington, DC},
publisher = {American Chemical Society},
reportid = {FZJ-2017-05856},
pages = {10514–10525},
year = {2017},
abstract = {Triosephosphate isomerase (TIM) is a proficient catalyst of
the reversible isomerization of dihydroxyacetone phosphate
(DHAP) to d-glyceraldehyde phosphate (GAP), via general base
catalysis by E165. Historically, this enzyme has been an
extremely important model system for understanding the
fundamentals of biological catalysis. TIM is activated
through an energetically demanding conformational change,
which helps position the side chains of two key hydrophobic
residues (I170 and L230), over the carboxylate side chain of
E165. This is critical both for creating a hydrophobic
pocket for the catalytic base and for maintaining correct
active site architecture. Truncation of these residues to
alanine causes significant falloffs in TIM’s catalytic
activity, but experiments have failed to provide a full
description of the action of this clamp in promoting
substrate deprotonation. We perform here detailed empirical
valence bond calculations of the TIM-catalyzed deprotonation
of DHAP and GAP by both wild-type TIM and its I170A, L230A,
and I170A/L230A mutants, obtaining exceptional quantitative
agreement with experiment. Our calculations provide a linear
free energy relationship, with slope 0.8, between the
activation barriers and Gibbs free energies for these
TIM-catalyzed reactions. We conclude that these clamping
side chains minimize the Gibbs free energy for substrate
deprotonation, and that the effects on reaction driving
force are largely expressed at the transition state for
proton transfer. Our combined analysis of previous
experimental and current computational results allows us to
provide an overview of the breakdown of ground-state and
transition state effects in enzyme catalysis in
unprecedented detail, providing a molecular description of
the operation of a hydrophobic clamp in triosephosphate
isomerase.},
cin = {ICS-6},
ddc = {540},
cid = {I:(DE-Juel1)ICS-6-20110106},
pnm = {551 - Functional Macromolecules and Complexes (POF3-551)},
pid = {G:(DE-HGF)POF3-551},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000407089500046},
pubmed = {pmid:28683550},
doi = {10.1021/jacs.7b05576},
url = {https://juser.fz-juelich.de/record/836814},
}