Prostate-Specific Membrane Antigen (PSMA), also known as Folate Hydrolase 1(FOLH1), is a type II transmembrane glycoprotein that acts as a prostate-specific integral membrane folate hydrolase and as a carboxypeptidase. PSMA is a useful marker for prostate tumors, both in diagnosis and prognosis. Although considered prostate-specific, PSMA expression has also been noted in the small intestine and in the brain. In the intestine, altered PSMA may be linked with impaired intestinal absorption of dietary folates and hyperhomocysteinemia. In the brain, the PSMA enzyme may be associated with glutamate cytotoxicity and associated pathological conditions. PSMA has been identified as a possible therapeutic target for prostate cancer.