May be involved in a signaling pathway during male germ cell development or mature sperm function. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by phosphorylation on Thr-168, potentially by autophosphorylation. Autophosphorylated. The mouse homolog is Stk22d. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.