Degrades proteins damaged by L-isoaspartyl residue formation (also known as beta-Asp residues). Also has L-asparaginase activity, which is used to liberate stored nitrogen during seed development. Cleavage of a beta-linked Asp residue from the N-terminus of a polypeptide. No activity for GlcNAc-Asn, Gly-L-Asn, L-Asp, L-Asn-alpha-amide, L-Gln or aspartylglucosamides. Heterotetramer of two alpha and two beta chains arranged as a dimer of alpha/beta heterodimers. Expressed in ripening seeds and developing nodules. 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. Subunit alpha overexpressed as a His-tagged protein where the His tag has the mass 2050. Subunit beta. Belongs to the Ntn-hydrolase family.