Mitogen-activated protein kinase (MAPK), part of the high-osmolarity glycerol (HOG) pathway (PubMed:26878695). With mpkC, plays a role in the osmotic and oxidative stress responses (PubMed:26878695). Involved in paradoxical growth, the cell wall integrity (CWI) pathway and biofilm formation (PubMed:26878695). SakA and mpkC collaborate during virulence and mpkC could act by modulating sakA activity upon exposure to several types of stresses and during cell wall biosynthesis (PubMed:26878695). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by threonine and tyrosine phosphorylation. Translocates to the nucleus upon osmotic stress and cell wall damage. Increases the sensitivity to osmotic and oxidative stresses as well as to cell wall damaging agents (PubMed:26878695). Affects virulence when mpkC is also deleted (PubMed:26878695). The single sakA deletion decreases mpkA phosphorylation and the double sakA/mpkC deletion abolishes mpkA phosphorylation (PubMed:26878695). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. MAP kinase subfamily.