Low-molecular-weight protein tyrosine phosphatase (LMW-PTP) is ~18kD protein which composes the fourth family of PTP. LMWPTP is cytoplasmic enzyme found in prokaryotes and eukaryotes. PTP conserved catalytic motif CXXXXXR is also present in LMWPTP, but it localized near the N-terminus. Several proteins have been found to be target of LMWPTP. For example, LMWPTP can dephosphorylate activated PDGF receptor and in turn modulate PDGF-induced mitogenesis. LMWPTP can target autophosphorylated epidermal growth factor receptor (EGFR) and plays a key role in regulating EGFR dependent transmembrane signaling. In addition, LMW-PTP can increase the cell proliferation rate in v-Ha-Ras-transformed cells (1).

Reference
1. Park, E.K., Warner, N., Mood, K., Pawson, T. and Daar, I.O. (2002) Low-molecular-weight protein tyrosine phosphatase is a positive component of the fibroblast growth factor receptor signaling pathway. Mol Cell Biol, 22, 3404-3414. PMID: 11971972