N-acetylated-alpha-linked acidic dipeptidase-like protein, also known as NAALADL1, NAALADase L, and Ileal dipeptidyl-peptidase, is a Single-pass type II membrane protein and a member of the peptidase M28 family and M28B subfamily. NAALADase L is mainly expressed in the distal small intestine. It is also expressed in the spleen and testis and Weakly expressed in the brain, locating mainly to the brain stem, amygdala, thalamus, and ventral striatum. NAALADase L is a chloride-activated, membrane-bound, metallopeptidase that cleaves the endogenous neuropeptide N-acetyl-aspartyl-glutamate (NAAG). NAAG acts as a partial NMDA agonist as well as a full agonist at the presynaptic metabotropic glutamate receptor 3 (mGluR3), where it acts to reduce glutamate release. NAALADase L also exhibits a dipeptidyl-peptidase IV type activity. NAALADase inhibition may be a novel therapeutic approach to reduce or inhibit heightened aggressiveness, and possibly to treat aggressive behavior associated with psychiatric disorders.