EC=2.7.11.24

Erk5, also known as BMK1 (big mitogen-activated kinase 1), has a TEY motif in the activation loop similar to Erk1/2, and shares high homology in the N-terminal kinase domain with Erk1/2. However, the long C-terminal domain makes Erk5 a unique MAP kinase. Erk5 is activated by a wide variety of extracellular signals, including tyrosine receptor kinases, G-protein-coupled receptors as well as osmotic and oxidative stress (1,2). The direct upstream kinase of Erk5 is defined as MEK5 (1). MEKK2, MEKK3 and Tpl-2 are all able to activate MEK5, depending on stimulus or cell background (3-5). Growing evidence indicates that the Erk5 pathway is involved in proliferation/differentiation regulation, oncogenesis and neuronal development (1,6-8).