The 107-1A4 monoclonal antibody specifically recognizes human Prostate-Specific Membrane Antigen (PSMA) which is also known as Glutamate carboxypeptidase II (GCPII), and N-acetyl-L-aspartyl-L-glutamate peptidase I (NAALADase I). PSMA is an ~100 kDa type II transmembrane glycoprotein. It is comprised of a large extracellular region with protease, apical and C-terminal domains that function in substrate binding and enzymatic activity, a transmembrane region, and a short intracellular N-terminal domain. PSMA is encoded by FOLH1 (Folate hydrolase 1) which belongs to the M28 peptidase family. PSMA is expressed in the brain and by cells in various tissues including the prostate, intestines, testis, bladder, liver, kidney, breast, and ovary. In the intestines, this enzyme functions as a folate hydrolase that cleaves glutamate from dietary folates to facilitate the cellular uptake of folic acid. Through its NAALADase activity, this enzyme also acts in the nervous system to hydrolyze the N-aceylaspartylglutamate (NAAG) neuropeptide into NAA and glutamate. This enzyme can thereby modulate excitatory neurotransmission with the release of glutamate which serves as an excitatory neurotransmitter. Overexpression of PSMA by cancer cells, such as prostate cancer cells, may allow for the increased uptake of folates required for rapid cellular division leading to tumor progression. PSMA expression has also been found by some urothelial adenocarcinoma cells and associated with the tumor neovasculature of some tumors as well. The 107-1A4 antibody reportedly recognizes a distinct conformational epitope in the PSMA extracellular domain.