regulatory subunit of Phosphorylase Kinase. The phosphorylase kinase holoenzyme consists of a polymer of 16 chains, four each of alpha, beta, gamma, and delta. Alpha and beta are regulatory chains, gamma is the catalytic chain, and delta is calmodulin. LOF mutations cause liver glycogenosis and one form of liver cirrhosis. Two alternatively spliced isoforms have been described. Note: This description may include information from UniProtKB.