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 and 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. Isoform 1 predominates in muscle, heart, brain and testis. Isoforms 1 and 2 are expressed in similar quantities in the other tissues. Isoform 3 is highly expressed in slow muscle and heart. Phosphorylation of Ser-1018 by PKA stimulates the dephosphorylation of the beta subunit and, thus, reverses the initial stimulation of PHK by the faster beta-subunit phosphorylation by PKA, that occurs in muscle in response to adrenaline. Cys-1234 is farnesylated, but the C-terminal tripeptide is not removed and the cysteine carboxyl is not methylated. Belongs to the phosphorylase b kinase regulatory chain family.