Tumor suppressor serine/threonine-protein kinase involved in synaptic plasticity, centriole duplication and G1/S phase transition. Polo-like kinases act by binding and phosphorylating proteins are that already phosphorylated on a specific motif recognized by the POLO box domains. Phosphorylates CENPJ, NPM1, RAPGEF2, RASGRF1, SNCA, SIPA1L1 and SYNGAP1. Plays a key role in synaptic plasticity and memory by regulating the Ras and Rap protein signaling: required for overactivity-dependent spine remodeling by phosphorylating the Ras activator RASGRF1 and the Rap inhibitor SIPA1L1 leading to their degradation by the proteasome. Conversely, phosphorylates the Rap activator RAPGEF2 and the Ras inhibitor SYNGAP1, promoting their activity. Also regulates synaptic plasticity independently of kinase activity, via its interaction with NSF that disrupts the interaction between NSF and the GRIA2 subunit of AMPARs, leading to a rapid rundown of AMPAR-mediated current that occludes long term depression. Required for procentriole formation and centriole duplication by phosphorylating CENPJ and NPM1, respectively. Its induction by p53/TP53 suggests that it may participate in the mitotic checkpoint following stress. 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 of Thr-239. Once activated, activity is stimulated by binding target proteins (By similarity). Interacts with NSF; causing NSF dissociation from GRIA2. Interacts with CIB1 (By similarity). Localizes to centrosomes during early G1 phase where it only associates to the mother centriole and then distributes equally to both mother and daughter centrioles at the onset of S phase. Expressed at higher level in the fetal lung, kidney, spleen and heart. Directly regulated by p53/TP53. Negatively regulated by miR-126. The POLO box domains act as phosphopeptide-binding module that recognize and bind serine-[phosphothreonine/phosphoserine]-(proline/X) motifs. PLK2 recognizes and binds docking proteins that are already phosphorylated on these motifs, and then phosphorylates them (By similarity). Catalytic activity is enhanced by phosphorylation of Thr-239. There are indications that PLK2 might act as a tumor suppressor: PLK2 is significantly down-regulated in a wide range of acute myeloid leukemias (AMLs) and B-cell lymphomas due to aberrant cytosine methylation in the CpG island located at the 5' of the PLK2 gene (PubMed:16160013, PubMed:21340720). Moreover, miR-126, a microRNA that negatively regulates PLK2 is up-regulated in AMLs, suggesting that PLK2 down-regulation by miR-126 could also contribute to leukemogenesis (PubMed:18832181). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. CDC5/Polo subfamily.