Catalyzes the hydrolytic cleavage of a subset of L-isoaspartyl (L-beta-aspartyl) dipeptides. Used to degrade proteins damaged by L-isoaspartyl residues formation. The best substrate for the enzyme reported thus far is iso-Asp-Leu. Binds 2 Zn(2+) ions per subunit. Has highest activity with Zn(2+) ions, but is also active with Co(2+) ions. P-hydroxymercuribenzoate causes a slight inhibition (8 to 17 %). Iodoacetamide, o-iodosobenzoate and ammonium persulfate do not inhibit the enzyme activity. Optimum pH is 7.5. Active over a wide pH range. Carboxylation allows a single lysine to coordinate two zinc ions (PubMed:12718528, PubMed:12946361, PubMed:15882050, PubMed:16289685). No observable phenotype. Does not result in reduced stationary phase or heat shock survival. Approximately 31% of the enzyme activity present. Belongs to the peptidase M38 family.