Essential for the two main proliferating life stages, the promastigotes and amastigotes, of the parasite. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Can use both Mg(2+) and Mn(2+) in vitro and shows higher activity with Mn(2+) but Mg(2+) is likely to be the in vivo cofactor. Optimum pH is 6-7. Expressed in promastigotes and to a lower extent in axenic amastigotes (at protein level) (PubMed:14636673, PubMed:16384531). Low expression levels in lesion-derived amastigotes (at protein level) (PubMed:14636673, PubMed:16384531). The TXY motif contains the threonine and tyrosine residues whose phosphorylation activates the MAP kinases. Dually phosphorylated on Thr-190 and Tyr-192, which activates the enzyme. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. MAP kinase subfamily.