Serine/threonine-protein kinase. Casein kinases are operationally defined by their preferential utilization of acidic proteins such as caseins as substrates. It can phosphorylate a large number of proteins. Participates in Wnt signaling. Regulates fast synaptic transmission mediated by glutamate (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Inhibited by triazolodiamine 1 (5-amino-3-([4-(aminosulfonyl)phenyl]amino)-N-(2,6-difluorophenyl)-1H-1,2,4-triazole-1-carbothioamide), (S)-propane-1,2-diol, 2-({6-[(3-chlorophenyl)amino]-9-isopropyl-9H-purin-2-yl}amino)-3-methylbutan-1-ol, N2-[(1R,2S)-2-aminocyclohexyl]-N6-(3-chlorophenyl)-9-ethyl-9H-purine-2,6-diamine and [4-amino-2-(3-chloroanilino)-1,3-thiazol-5-yl](4-fluorophenyl)methanone. Monomer. Autophosphorylated. Belongs to the protein kinase superfamily. CK1 Ser/Thr protein kinase family. Casein kinase I subfamily.