Has both folate hydrolase and N-acetylated-alpha-linked-acidic dipeptidase (NAALADase) activity. Has a preference for tri-alpha-glutamate peptides (By similarity). In the intestine, required for the uptake of folate. In the brain, modulates excitatory neurotransmission through the hydrolysis of the neuropeptide, N-aceylaspartylglutamate (NAAG), thereby releasing glutamate. Also exhibits a dipeptidyl-peptidase IV type activity. In vitro, cleaves Gly-Pro-AMC. 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. The NAALADase and folate hydrolase activities are inhibited by quisqualic acid. Homodimer. Expressed predominantly in the hippocampal region of the brain and in kidney. Lower levels in the ovary, testis and mandibular gland. 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. There are amino acid differences between the sequence shown in fig.1 (PubMed:11210180) and the sequence deposited in the database (AF026380). The sequence from fig.1 shows only 3 conflicts between PubMed:11210180 and PubMed:16141072. These are at AA positions 141, 240 and 287.