{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Protein gene product 9.5 (PGP 9.5), also known as ubiquitin carboxyl-terminal hydrolase-1 (UCH-L1), is a 27-kDa enzyme originally isolated from whole brain extracts. PGP 9.5 acts as a deubiquitinase in the ubiquitin system, involved in protein degradation, turnover, and recycling. Although PGP 9.5 expression in normal tissues was originally thought to be strictly confined to neurons and neuroendocrine cells, it has been subsequently documented in distal renal tubular epithelium, spermatogonia, Leydig cells, oocytes, melanocytes, prostatic secretory epithelium, ejaculatory duct cells, epididymis, mammary epithelial cells, Merkel cells, and dermal fibroblasts. According to literature, PGP 9.5 is also expressed in various mesenchymal neoplasms."}]}]}