Enables protein serine/threonine kinase activity. Involved in several processes, including cellular hypotonic response; negative regulation of transport; and protein phosphorylation. Acts upstream of or within several processes, including negative regulation of potassium ion transmembrane transport; negative regulation of protein phosphorylation; and regulation of inflammatory response. Located in apical plasma membrane and basolateral plasma membrane. Is expressed in brain and metanephros. Used to study Gitelman syndrome and pseudohypoaldosteronism. Orthologous to human STK39 (serine/threonine kinase 39). [provided by Alliance of Genome Resources, Apr 2022]