The PHKA1 gene encodes the alpha subunit of muscle phosphorylase kinase (EC 2.7.1.38), a key regulatory enzyme of glycogen metabolism. Phosphorylase kinase consists of 4 copies of an alpha-beta-gamma-delta tetramer. The alpha, beta (PHKB; MIM 172490), and gamma (PHKG1; MIM 172470 and PHKG2; MIM 172471) subunits have several isoforms; the delta subunit is calmodulin (CALM1; MIM 114180). PHKA2 (MIM 306000) encodes the alpha subunit of liver-specific phosphorylase kinase and is also located on the X chromosome.[supplied by OMIM]
