Calcium-dependent protein kinase which acts as a sensor and effector of intracellular Ca(2+) levels (By similarity). In sporozoites, probably involved in the secretion of the cysteine protease that cleaves circumsporozoite protein CSP, thereby exposing CSP TSR domain, which binds with high affinity to highly sulfated heparan sulfate proteoglycans (HSPGs), resulting in productive invasion of the host hepatocytes (PubMed:18005753). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by calcium. The EF-hand domains 1, 4 and 6 appear to lack a functional calcium binding site. It is unclear if CDPK6 has the junction domain (J domain) found in other CDPKs. Sporozoites display enhanced migratory activity and are less infective for host hepatocytes (PubMed:18005753). Severe decrease in circumsporozoite protein CSP proteolytic cleavage upon sporozoite contact with host hepatocytes (PubMed:18005753). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. CDPK subfamily.