Who is LYP?
Protein tyrosine phosphatase non-receptor type 22 (PTPN22) is a cytoplasmatic protein encoded by gene PTPN22 and a member of PEST family of protein tyrosine phosphatases. This protein is also called "PEST-domain Enriched Phosphatase" ("PEP") or "Lymphoid phosphatase" ("LYP"). The name LYP is used strictly for the human protein encoded by PTPN22, but the name PEP is used only for its mouse homolog. However, both proteins have similar biological functions and show 70% identity in amino acid sequence. PTPN22 functions as a negative regulator of T cell receptor (TCR) signaling, which maintains homeostasis of T cell compartment.