Protein phosphatases: function and regulation

Thousands of proteins are expressed in a typical mammalian cell, of which a third are now thought to contain covalently bound phosphate. About 200 protein kinases and 100 protein phosphatases have already been identified. Whereas the classification, properties and regulation of protein kinases are largely studied, the information about the protein phosphatase is far to be completed. Relatively better is studied a group of serine/treonine protein phosphatases. It has been discovered that besides the control of the key enzymes of metabolic pathways, these phosphatases participate in the regulation of gene transcription and cell division in eukariots. In addition, the identification of tyrosine protein phosphatases points to a novel intracellular signalling pathways, controlling cell-cell communication, cell proliferation and signal transduction of receptors for peptide hormones and growth factors. The recent progress in these families of protein phosphatases is the topic of present review.