Catalysis of the concomitant phosphorylation of threonine (T) and tyrosine (Y) residues in a Thr-Glu-Tyr (TEY) thiolester sequence in a MAP kinase (MAPK) substrate. [ https://www.worldcat.org/search?q=bn%3A0198547684 ]

Synonyms: ERK activator kinase activity MAPK activator activity MAPKK activity

This is just here as a test because I lose it