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. Homodimer. Expressed ovary, testes and lung, but not brain. 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.