Phosphorylase b kinase catalyzes the phosphorylation of serine in certain substrates, including troponin I. The beta chain acts as a regulatory unit and modulates the activity of the holoenzyme in response to phosphorylation. By phosphorylation of various serine residues. 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. Cys-1090 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.