Acts in asparagine catabolism but also in the final steps of protein degradation via hydrolysis of a range of isoaspartyl dipeptides. Cleavage of a beta-linked Asp residue from the N-terminus of a polypeptide. Heterotetramer of two alpha and two beta chains arranged as a dimer of alpha/beta heterodimers. Cleaved into an alpha and beta chain by autocatalysis; this activates the enzyme. The N-terminal residue of the beta subunit is responsible for the nucleophile hydrolase activity (By similarity). May be due to intron retention or to a competing acceptor splice site. Belongs to the Ntn-hydrolase family.