Muscle phosphorylase kinase deficiency

Phosphorylase kinase (PhK) is a serine/threonine-specific protein kinase which activates glycogen phosphorylase to release glucose-1-phosphate from glycogen. PhK phosphorylates glycogen phosphorylase at two serine residues, triggering a conformational shift which favors the more active glycogen phosphorylase “a” form over the less active glycogen phosphorylase b.The protein is a hexadecameric holoenzyme—that is, a homotetramer in which each subunit is itself a tetramer—arranged in an approximate “butterfly” shape. [Source: Wikipedia ]