Calcium/calmodulin-dependent protein kinase belonging to a proposed calcium-triggered signaling cascade. In vitro phosphorylates CREB1 and SYN1/synapsin I. Phosphorylates and activates CAMK1 (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by Ca(2+)/calmodulin. Expressed at highest levels in adult brain, and expressed in embryo. In the adult brain detected at high levels in the anterior olfactory nuclei, piriform cortex, septal nuclei, bed nuclei of the stria terminalis, hippocampal pyramidal cells, dentate granule cells, amygdala, hypothalamic nuclei, parabrachial nucleus, and nucleus of the solitary tract. Expressed at lower levels in adult ovary and heart and at very low levels in testis, lung and muscle. During embryogenesis detected at 10 dpc and expression gradually increases thereafter. Expressed mainly in the nervous system, including brain, spinal cord, trigeminal ganglion, and retina. Within the CNS detected in the mantle zone, but not in the ventricular zone. Detected at postnatal day 23 with highest levels in mesencephalon. Also expressed in developing bone and gut. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. CaMK subfamily.