Serine/threonine kinase which is involved in male germ cell development and in mature sperm function (By similarity). May be involved in the Cre/Creb signaling pathway (By similarity). Phosphorylates CREB1 on 'Ser-133' in vitro and can stimulate Cre/Creb pathway in cells (PubMed:15964553). Phosphorylates CREM on 'Ser-116' in vitro (By similarity). Phosphorylates ODF2 on 'Ser-95' (By similarity). . This is the function of TSSK4 (testis specific serine kinase 4, Ensembl gene identifier ENSG00000139908).