Protein kinase C also known as PKC (EC 2.7.11.13) is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and threonine amino acid residues on these proteins. PKC enzymes in turn are activated by signals such as increases in the concentration of diacylglycerol (DAG) or calcium ions (Ca²⁺). Hence PKC enzymes play important roles in several signal transduction cascades.