Peptidase M28 family; Plasma glutamate carboxypeptidase (PGCP; blood plasma glutamate carboxypeptidase; EC 3.4.17.21) subfamily. PGCP is a 56kDa glutamate carboxypeptidase that is mainly produced in mammalian placenta and kidney, the majority of which is thought to be secreted into the bloodstream. Similar proteins are also found in other species, including bacteria. These proteins contain protease-associated (PA) domain inserts between the first and second strands of the central beta sheet in the protease-like domain. The PA domains may participate in substrate binding and/or promoting conformational changes, which influence the stability and accessibility of the site to substrate. The exact physiological substrates of PGCP are unknown, although this enzyme may play an important role in the hydrolysis of circulating peptides. Its closest homolog encodes an important brain glutamate carboxypeptidase II (NAALADase) identical to the prostate-specific membrane antigen (PSMA), which serves as a marker for prostatic cancer metastasis. Hypermethylation of PGCP gene has been associated with human bronchial epithelial (HBE) cell immortalization and lung cancer. PGCP also provides an attractive target for serological analysis in hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) patients.
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