Acts in asparagine catabolism but also in the final steps of protein and degradation via hydrolysis of a range of isoaspartyl dipeptides. The affinity for Asn and at least 4 isoaspartyl dipeptides (L-beta-Asp-Ala, L-beta-Asp-Gly, L-beta-Asp-Leu, L-beta-Asp-Phe) is quite low, KM being greater than 4.0 mM. The enzyme is inactive on alpha-aspartyl 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. A number of isoforms are produced. According to EST sequences. 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. Belongs to the Ntn-hydrolase family.