Acylamino-acid-releasing enzyme (AARE) can efficiently liberate the N-terminal acetylamino acid from N-acetylated peptides of up to about 30 residues in length. It does not act on intact N-acetylated proteins. Release of the N-acetylamino acid from proteins is required for Edman-degradation-based sequence analysis. Fragmentation of proteins with residue-specific proteases followed by the release of the N-acetylamino acid from the isolated peptides (using AARE), is required to facilitate N-terminal sequence analysis of proteins.