Has N-acetylated-alpha-linked-acidic dipeptidase (NAALADase) activity. Also exhibits a dipeptidyl-peptidase IV type activity. Inactivates the peptide neurotransmitter N-acetylaspartylglutamate. Release of an unsubstituted, C-terminal glutamyl residue, typically from Ac-Asp-Glu or folylpoly-gamma-glutamates. Binds 2 Zn(2+) ions per subunit. Required for NAALADase activity. Inhibited by quisqualate. Homodimer. Highest expression in the testis. Also found in ovary and spleen. Weak expression in prostate, heart and placenta. In brain, expressed in striatum, parietal cortex and ventral striatum with lower levels in hippocampus, brain stem, putamen and superior colliculus. The NAALADase activity is found in the central region, the dipeptidyl peptidase IV type activity in the C-terminal. Belongs to the peptidase M28 family. M28B subfamily.