Protein kinase C (PKC) is a calcium-activated, 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. 

Protein Kinase C beta (PKC beta) is an 80 kDa member of the conventional group (cPKCs: sensitive to diacylglycerol, phosphotidylserine and phorbol esters) of the PKC family of serine/threonine kinases that are involved in a wide range of physiological processes including mitogenesis, cell survival, transcriptional regulation and tumor promotion. PKC beta has been implicated in diabetes and carcinogenesis. PKC beta isoforms 1 & 2 are phosphorylated on three sites, threonine 500 in the activation loop, beta 1 threonine 642 (beta 2 641) in the turn loop and beta 1 serine 661 (beta 2 660) in the hydrophobic loop. Phosphorylation of PKC beta 1 & 2 on threonine 500 by PDK1 is a prerequisite for its autophosphoylation and catalytic competence.