In vitro; can phosphorylate exogenous substrates on Ser and Thr residues. May have a physiological role in development being involved in cellular growth and differentiation. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Autophosphorylates on Tyr-356 and Tyr-358. Highly expressed and active during embryogenesis and pupation and at lower levels in larva and adult. Phosphorylated on serine/threonine residues. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. MNB/DYRK subfamily. Deletion within an exon that does not correspond to an intron.