Peptidase M28 family; prostate-specific membrane antigen (PSMA, also called glutamate carboxypeptidase II or GCP-II)-like subfamily. PSMA is a homodimeric type II transmembrane protein containing three distinct domains: protease-like, apical or protease-associated (PA) and helical domains. The protease-like domain is a large extracellular portion (ectodomain). PSMA is over-expressed predominantly in prostate cancer (PCa) as well as in the neovasculature of most solid tumors, but not in the vasculature of the normal tissues. PSMA is considered a biomarker for PCa and possibly for use as an imaging and therapeutic target. The extracellular domain of PSMA possesses two unique enzymatic functions: N-acetylated, alpha-linked acidic dipeptidase (NAALADase) which cleaves terminal glutamate from the neurodipeptide N-acetyl-aspartyl-glutamate (NAAG), and folate hydrolase (FOLH) which cleaves the terminal glutamates from gamma-linked polyglutamates (carboxypeptidase). A mutation in this gene may be associated with impaired intestinal absorption of dietary folates, resulting in low blood folate levels and consequent hyperhomocysteinemia. Expression of this protein in the brain may be involved in a number of pathological conditions associated with glutamate excitotoxicity. Inhibition of GCP-II has been shown to be effective in preclinical models of neurological disorders associated with excessive activation of glutamatergic systems. This gene likely arose from a duplication event of a nearby chromosomal region. Alternative splicing gives rise to multiple transcript variants.
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