TESK2 is a dual specificity protein kinase activity catalyzing autophosphorylation and phosphorylation of exogenous substrates on both serine/threonine and tyrosine residues. TESK2 phosphorylates cofilin at Ser-3. It may play an important role in spermatogenesis. This nuclear enzyme is thought to be activated by autophosphorylation on Ser-219. Expression is predominantly in testis and prostate, with highest concentrations in nongerminal Sertoli cells.