Conformer Selection and Intensified Dynamics During Catalytic Turnover in Chymotrypsin

摘要

During catalytic turnover, enzymes undergo thermally driven conformational fluctuations (dynamics) that are directly linked to catalytic efficiency.In broad terms, this link exists because enzymes must sample specific dynamic modes in order to access high-energy structures along the catalytic reaction coordinate. Mass spectrometry-based approaches for probing enzyme dynamics are developing rapidly, but have been limited thus far by the application of H/D exchange (HDX) under steady-state conditions, which results in averaging of the data over multiple catalytic states. Models that attempt to define the specific nature of the enzyme dynamics/activity relationship are therefore drawn overwhelmingly from Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR experiments on "active" enzymes. This approach is extremely powerful, but is confined to a small set of highly reversible reactions in order to circumvent the issue of substrate depletion during the experiment.