Serine/threonine-protein kinase which, in association with cye-1, regulates proliferation, quiescent state and cell fate during the development of several cell lineages (PubMed:17115027. PubMed:17476329). In the embryo, initiates the establishment of cell polarity through the recruitment of the centrosomal proteins spd-2 and spd-5 during prophase (PubMed:17115027). Phosphorylation and inhibition of the translational repressor gld-1 by the cdk-2/cye-1 complex regulates the pool of germline stem cells and the size of the mitotic zone in the gonads by preventing entry into meiosis (PubMed:21455289). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Binds 2 Mg(2+) ions. Interacts with cye-1 (By similarity); the interaction likely regulates cdk-2 activity and is probably required for gld-1 phosphorylation. RNAi-mediated knockdown causes arrest at various developmental stages. The few animals reaching adulthood are sterile and have a protruding vulva (PubMed:10207147). Gonads have an abnormal mitotic zone characterized by an enlargement of the distal germ cell nuclei, a reduction in the number of mitotic germ cells, a reduction in the mitotic region length and abnormal expression of gld-1 (PubMed:21455289). Embryos have persistent ruffling throughout the cortex and mislocalization of par-2, which remains cytoplasmic, and par-6, which remains distributed throughout the cortex. In 33 percent of embryos the first division is symmetric (PubMed:17115027). Production of 2 additional distal tip cells (DTC) during larval development (PubMed:17476329). RNAi-mediated knockdown in embryos causes a slight delay in cell cycle progression (PubMed:17115027). Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.