Protein kinase that plays a role in vesicle-mediated transport processes and exocytosis. Can phosphorylate CCNY at 'Ser-336' (in vitro) (By similarity). Plays a role in the regulation of insulin secretion in response to changes in blood glucose levels. Regulates GH1 release by brain neurons. Phosphorylates NSF, and thereby regulates NSF oligomerization. Required for normal spermatogenesis. Regulates neuron differentiation and dendrite development. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Found in a complex containing CABLES1, CDK17 and TDRD7. Interacts with BRSK2. Identified in a complex with NSF, syntaxin-1, synaptotagmin, SYN1, SYP and CDK5R1 (By similarity). Interacts with YWHAH, YWHAQ and YWHAZ. Interacts with CCNY; this increases the CDK16 kinase activity. Interacts with NSF. Colocalizes with insulin in pancreas islets. Highly expressed in testis and brain, and detected at lower levels in heart, skeletal muscle, adipose tissue, lung, spleen and pancreas (at protein level). Ubiquitous with highest levels in testis and brain, with longer form predominant in all tissues except the testis. Phosphorylation at Ser-153 inhibits kinase activity. No visible phenotype in females; they are viable and fertile. Male mice are infertile, due to a defect in late stages of spermatogenesis. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.