Mechanisms of Catalysis
The favoured model for the enzyme–substrate interaction is the
induced fit model. This model proposes that the initial interaction
between enzyme and substrate is relatively weak, but that these weak
interactions rapidly induce conformational changes in the enzyme that
strengthen binding. Mechanisms of catalysis include catalysis by bond
strain; by proximity and orientation; by active-site proton donors or
acceptors; covalent catalysis and quantum tunnelling.
Enzyme kinetics cannot prove which modes of catalysis are used by an
enzyme. However, some kinetic data can suggest possibilities to be
examined by other techniques. For example, a ping–pong mechanism
with burst-phase pre-steady-state kinetics would suggest covalent
catalysis might be important in this enzyme's mechanism. Alternatively,
the observation of a strong pH effect on Vmax but not KM might
indicate that a residue in the active site needs to be in a particular
ionisation state for catalysis to occur.
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