This is calcium-independent, phospholipid-dependent, serine- and threonine-specific enzyme. PKC is activated by diacylglycerol which in turn phosphorylates a range of cellular proteins. PKC also serves as the receptor for phorbol esters, a class of tumor promoters (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Requires high levels of phosphatidylserine to be activated. The presence of the C2 domain lowers the affinity of protein kinase C activators for the C1 domains and this inhibition can be removed by phosphatidylserine. Phosphatidic acid, however, is much more potent than phosphatidylserine in reducing C2 domain-mediated inhibition, suggesting that phosphatidic acid may be a required cofactor for the activation of APL II. Expressed in nervous tissues, ovotestis and gut. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. PKC subfamily.