ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Stimulated about twofold by phospholipids or phorbol esters. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. PKC subfamily.