Classical tyrosine-specific PTPs include both cytosolic and transmembrane receptor-like proteins, among which several enzymes were identified and validated as drug targets, such as PTP1B, TCPTP, SHP2, CD45; alterations or deregulation of these PTPs were shown to play crucial roles in the pathogenesis of different human diseases, including diabetes, cancer, autoimmune and neurological disorders. Here, PTPN11 is linked to diabetes mellitus.