Final answer:
An irreversible inhibitor inactivates an enzyme by covalently bonding to the active site. It decreases Vmax, the maximum rate of the reaction, while leaving Km, the substrate concentration for half of Vmax, unchanged.
Step-by-step explanation:
An irreversible inhibitor inactivates an enzyme by bonding covalently to a particular group at the active site. This covalent bond cannot be dissociated, making the inhibition permanent and irreversible. The irreversible inhibitor blocks the enzyme's active site, preventing the substrate from binding and catalysis from occurring.
In the presence of an irreversible inhibitor, the maximum rate of the enzyme-catalyzed reaction (Vmax) decreases. This is because the inhibitor permanently inactivates the enzyme, limiting the number of active enzyme molecules available for catalysis. However, the Michaelis-Menten constant (Km), which represents the substrate concentration at which the reaction rate has reached half of Vmax, remains unchanged. This means that the affinity of the enzyme for the substrate remains the same.
In summary, the kinetics of an enzyme-catalyzed reaction are affected by an irreversible inhibitor by decreasing Vmax while leaving Km unchanged.