Phosphorylase b kinase catalyzes the phosphorylation of serine in certain substrates, including troponin I. The alpha chain may bind calmodulin. By phosphorylation of various serine residues. Allosteric regulation by calcium. Glycan biosynthesis; glycogen metabolism. Hexadecamer of 4 heterotetramers, each composed of alpha, beta, gamma, and delta subunits. Alpha (PHKA1 or PHKA2) and beta (PHKB) are regulatory subunits, gamma (PHKG1 or PHKG2) is the catalytic subunit, and delta is calmodulin. Muscle specific. Isoform 1 is predominant in vastus lateralis muscle. Isoform 2 predominates slightly in heart, and it predominates clearly in the other tissues tested. Although the final Cys may be farnesylated, the terminal tripeptide is probably not removed, and the C-terminus is not methylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the phosphorylase b kinase regulatory chain family.