EC=2.7.11.24

P38 MAP kinase (MAPK), also called RK (3) or CSBP (2), is the mammalian homologue of the yeast HOG kinase and participates in a signaling cascade controlling cellular responses to cytokines and stress (1-4). Four isoforms of p38 MAP kinase, alpha, beta, gamma and delta, have been identified so far. Like the SAPK/JNK pathway, p38 MAP kinase is activated by a variety of cellular stresses including osmotic shock, inflammatory cytokines, lipopolysaccharides (LPS), UV light and growth factors (1-5). MKK3 and SEK activate p38 MAP kinase by phosphorylation at threonine 180 and tyrosine 182. Activated p38 MAP kinase has been shown to phosphorylate and activate MAPKAP kinase 2 (3) and to phosphorylate the transcription factors ATF-2 (5), Max (6) and MEF2 (5-8). Nonphosphorylated p38 MAP Kinase Control Cell.