Protein tyrosine dephosphorylation and signal transduction

The protein tyrosine phosphatases comprise a family of enzymes that specifically dephosphorylate tyrosyl residues. Determination of the amino acid sequence of a major low molecular mass form isolated from human placenta (PTPase 1B) provided the basis for the first identification of transmembrane proteins that bear intracellular phosphatase domains. The existence of such molecules, bearing the hallmarks of receptors, raises the exciting possibility of a novel mechanism of signal transduction in which the early events involve the ligand-induced dephosphorylation of tyrosyl residues in proteins.