Myophosphorylase

phosphorylase, glycogen; muscle (McArdle syndrome, glycogen storage disease type V)
Myophosphorylase
Identifiers
Symbol	PYGM
Entrez	5837
HUGO	9726
OMIM	608455
RefSeq	NM_005609
UniProt	P11217
Other data
EC number	2.4.1.1
Locus	Chr. 11 q12-q13.2

Myophosphorylase is the muscle isoform of the enzyme glycogen phosphorylase. This enzyme helps break down glycogen (a form of stored carbohydrate) into glucose-1-phosphate (not glucose), so that it can be utilized within the muscle cell.

A deficiency is associated with Glycogen storage disease type V, also known as "McArdle's Syndrome".

A case study suggested that a deficiency in myophosphorylase may be linked with cognitive impairment. Besides muscle, this isoform is present in astrocytes, where it plays a key role in neural energy metabolism. A 55-year-old woman with McArdle disease has expressed cognitive impairment with bilateral dysfunction of prefrontal and frontal cortex. Further studies are needed to assess the validity of this claim.