PTS and diabetes mellitus: 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.