EC=2.7.11.24

Mitogen Activated Protein Kinases (MAPKs) play pivotal roles in mediating signal transduction from the cell surface to the nucleus. These kinases are encoded by distinct genes and together form a family of kinases whose activation is dependent upon dual phosphorylation on specific threonine and tyrosine residues. In yeast, a number of different MAP Kinases have been identified and are activated by distinct signaling pathways. In mammalian cells, the best characterized sub-group of the MAP Kinase family are the Extracellular Signal Regulated Kinases (ERKs). To date, at least 4 distinct ERKs have been identified including: ERK1 (p44/p43), ERK2 (p42/p43), ERK3 (p62), and ERK4 (p45). Analysis of cDNAs encoding MAP Kinase suggest that numerous other ERKs may exist. MAP Kinase has been shown to phosphorylate numerous proteins including: RSK (2), c-Fos, c-Jun, c-Myc, c-raf, MAP2, and MEK (3). MAP Kinase is directly activated when phosphorylated by MEK and indirectly stimulated by many factors (4,5,6).