Abstract
Proteins are complex systems so that their reactions may have
characteristics not often observed in small molecules. Two common
aspects of small molecule reactions are an exponential time dependence
and Arrhenius-like temperature dependence. This review shows that
corresponding behavior is not always observed in reactions involving
proteins. Bond-making and bond-breaking reactions, as well as
conformational changes, which do not involve chemical bonds, are
discussed. As examples of bond making, bond breaking reactions, enzyme
catalysis by triosephosphate isomerase and ligand binding by myoglobin
are considered. Several reactions involving conformational changes are
described. They include aromatic side chain rotations, loop/lid opening
and closing motions, quaternary structural changes in hemoglobin, and
protein folding. In some of these cases, deviations from simple small
molecule behavior have been observed, but it is evident that more
information is needed for a complete understanding. The protein folding
reaction, which is most complex because it involves the entire
polypeptide chain, is analyzed in some detail.
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