Protein kinase C (PKC) is a family of lipid-activated enzymes, contributing to signal transduction networks that co-ordinate a wide range of cellular functions, and almost all aspects of immune cell function, so are considered crucial immune regulators.

Divided into three subfamilies [1]:
Conventional PKCs- activated by phorbol 12-myristate 13-acetate and diacylglycerol (Ca²⁺ sensitive)- PKCs α, βI, βII, γ
Novel PKCs- activated by diacylglycerol- PKCs δ, θ, ε, η
Atypical PKCs- insensitive to both Ca²⁺ and diacylglycerol- PKCs ζ, ι/λ

All members contain a conserved kinase domain, and variable regulatory domains which contain C1 domains which act as ligand sensors. Isoform-specific subcellular compartmentalization patterns, protein-protein interactions, and posttranslational modifications affecting catalytic function confer unique functions in cells.

All subfamilies are expressed in T cells.

1. Steinberg SF. (2008) Structural basis of protein kinase C isoform function. Physiol Rev, 88 (4): 1341-78. [PMID:18923184]