Catalysis of the phosphorylation and activation of a MAP kinase kinase; each MAP kinase kinase can be phosphorylated by any of several MAP kinase kinase kinases
1. PMID 95612672. EC 2.7.11.253. MetaCyc 2.7.11.25-RXN4. Reactome: R-HSA-168184 "Activated TAK1 mediates phosphorylation of the IKK Complex"
5. Reactome: R-HSA-2730887 "Autophosphorylation and activation of MEKK1"
6. Reactome: R-HSA-392530 "p-S400-Cot phosphorylates NIK"
7. Reactome: R-HSA-450337 "Activated TAK1 phosphorylates MKK4/MKK7"
8. Reactome: R-HSA-450346 "activated human TAK1 phosphorylates MKK3/MKK6"
9. Reactome: R-HSA-451649 "TPL2 phosphorylates MEK1, SEK1"
10. Reactome: R-HSA-727819 "TAK1 phosphorylates MKK6"
11. Reactome: R-HSA-933530 "Activation of IKK by MEKK1"