Catalytic domain of the Serine/Threonine Kinases, Mitogen-Activated Protein Kinase Kinase Kinases 12 and 13
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. MAP3K12 is also called MAPK upstream kinase (MUK), dual leucine zipper-bearing kinase (DLK) or leucine-zipper protein kinase (ZPK). It is involved in the c-Jun N-terminal kinase (JNK) pathway that directly regulates axonal regulation through the phosphorylation of microtubule-associated protein 1B (MAP1B). It also regulates the differentiation of many cell types including adipocytes and may play a role in adipogenesis. MAP3K13, also called leucine zipper-bearing kinase (LZK), directly phosphorylates and activates MKK7, which in turn activates the JNK pathway. It also activates NF-kB through IKK activation and this activity is enhanced by antioxidant protein-1 (AOP-1). MAP3Ks (MKKKs or MAPKKKs) phosphorylate and activate MAP2Ks (MAPKKs or MKKs), which in turn phosphorylate and activate MAPKs during signaling cascades that are important in mediating cellular responses to extracellular signals. The MAP3K12/13 subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.