Protein-tyrosine phosphatase 1B (PTP-1B), a member of the protein tyrosine phosphatase (PTP) catalyzes the hydrolysis of the phosphate monoesters specifically in tyrosine residues. Members of the PTP family share a highly conserved catalytic motif, which is essential for the catalytic activity. PTPs are known to be signaling molecules that regulate a variety of cellular processes including cell growth, differentation,Mouse,itotic cycle, and oncogenic transformation. PTP-1B acts as a negative regulator of insulin signaling by dephosphorylating the phosphotyrosine residues of insulin receptor kinase. PTP-1B dephosphorylates epidermal growth factor kinase as well as JAK2 and TYK2 kinases in cell growth control and cell response to interferon stimulation. PTP-1B plays an important role in CKII- and p60c-src-induced signal tranduction cascades.