Which type of inhibitor binds covalently to enzyme side chains and is typically irreversible?

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Inhibition that forms a covalent bond with enzyme side chains and is typically irreversible means the enzyme is permanently inactivated by a chemical modification. Irreversible inhibitors create a covalent link to reactive amino acid residues in the enzyme’s active site—such as serine, cysteine, or lysine—so the site is permanently altered and can no longer catalyze the reaction. Because the bond is covalent, simply adding more substrate won’t restore activity; the enzyme must be replaced through new synthesis. This contrasts with reversible inhibitors, which bind non-covalently and can dissociate, allowing activity to return. Competitive inhibitors also bind at the active site but do so reversibly, while non-competitive inhibitors bind elsewhere and reduce activity without permanently changing the active site.