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phosphorylase, glycogen; muscle (McArdle syndrome, glycogen storage disease type V)
Symbol PYGM
Entrez 5837
HUGO 9726
OMIM 608455
RefSeq NM_005609
UniProt P11217
Other data
EC number
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 it can be used within the muscle cell.

Clinical significance[edit]

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.[2]


  1. ^ "RCSB Protein Data Bank - Structure Summary for 3MSC - Glycogen phosphorylase complexed with 2-nitrobenzaldehyde-4-(beta-D-glucopyranosyl)-thiosemicarbazone". 
  2. ^ Mancuso M, Orsucci D, Volterrani D, Siciliano G (March 2011). "Cognitive impairment and McArdle disease: Is there a link?". Neuromuscul Disord. 21 (5): 356–8. doi:10.1016/j.nmd.2011.02.013. PMID 21382715. 

External links[edit]