Degrades proteins damaged by L-isoaspartyl residue formation (also known as beta-Asp residues). Degrades L-isoaspartyl-containing di- and maybe also tripeptides. Also has L-asparaginase activity, although this may not be its principal function. May be involved in glutathione, and possibly other peptide, transport, although these results could also be due to polar effects of disruption. 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, aspartylglucosamides alpha- or gamma-aspartyl dipeptides. Heterotetramer of two alpha and two beta chains arranged as a dimer of alpha/beta heterodimers. Repressed by cysteine, an effect that is attributed to CysB. Autocleaved. Generates the alpha and beta subunits. The N-terminal residue of the beta subunit is thought to be responsible for the nucleophile hydrolase activity. Both subunits undergo further processing at their C-termini. The overexpressed alpha subunit seems to consist of residues 2-161, with an oxidized Met residue and a tightly coordinated Na(+), whereas the overexpressed beta subunit is processed to residue 315 and has 3 oxidized Met residues. Processing of the alpha subunit is inhibited by Zn(2+). Subunit alpha. Subunit beta. Belongs to the Ntn-hydrolase family.