Glutamate carboxypeptidase 2, also known as Glutamate carboxypeptidase II, Membrane glutamate carboxypeptidase, Prostate-specific membrane antigen, GCPII, PSMA, FOLH1, and NAALAD1, is a single-pass type I I membrane protein which belongs to the peptidase M28 family and M28B subfamily. FOLH1 is highly expressed in prostate epithelium. It is detected in urinary bladder, kidney, testis, ovary, fallopian tube, breast, adrenal gland, liver, esophagus, stomach, small intestine, colon, brain (at protein level), and the capillary endothelium of a variety of tumors. FOLH1 has both folate hydrolase and N-acetylated alpha linked acidic dipeptidase (NAALADase) activity. It has a preference for tri-alpha-glutamate peptides. Genetic variation in FOLH1 may be associated with low folate levels and consequent hyperhomocysteinemia. This condition can result in increased risk of cardiovascular disease, neural tube defects, and cognitive deficits. FOLH1 also shows a promising role in directed imaging and therapy of recurrent or metastatic disease.