Myophosphorylase
Encyclopedia
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.
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
glycogen phosphorylase
Glycogen phosphorylase
Glycogen phosphorylase is one of the phosphorylase enzymes . Glycogen phosphorylase catalyzes the rate-limiting step in the degradation of glycogen in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond...
.
This enzyme helps break down glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
(a form of stored carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
) into glucose-1-phosphate
Glucose-1-phosphate
Glucose 1-phosphate is a glucose molecule with a phosphate group on the 1'-carbon.-Catabolic:In glycogenolysis, it is the direct product of the reaction in which glycogen phosphorylase cleaves off a molecule of glucose from a greater glycogen structure.To be utilized in cellular catabolism it must...
, (not glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
) so that it can be utilized within the muscle cell.
A deficiency is associated with Glycogen storage disease type V
Glycogen storage disease type V
Glycogen storage disease type V is a metabolic disorder, more specifically a glycogen storage disease, caused by a deficiency of myophosphorylase. Its incidence is reported as 1 in 100,000, approximately the same as glycogen storage disease type I....
, 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.