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. Heterotetramer of two alpha and two beta chains arranged as a dimer of alpha/beta heterodimers. Developing seeds. 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). Belongs to the Ntn-hydrolase family.