Phosphorylase kinase (PhK) deficiency causing glycogen storage disease type IX (GSD IX) results from deficiency of the enzyme phosphorylase b kinase, which has a major regulatory role in the breakdown of glycogen. For more, see Causes/Inheritance. Phosphorylase deficiency causes exercise intolerance, such as cramps, muscle pain and weakness, shortly after beginning exercise. Muscle Glycogen Phosphorylase Deficiency Preferred Term. Lactate may be used as a fuel source once converted to pyruvate. Additional and Relevant Useful Information for Muscular Phosphorylase Kinase Deficiency Disorder: Muscular Phosphorylase Kinase Deficiency is also known by the following names: Debranching enzyme. These require urgent assessment for rhabdomyolysis as in about 30% of cases this leads to acute kidney injury. The disease is caused by a genetic defect in the phosphorylase (also known as myophosphorylase) enzyme, which affects the breakdown of glocogen, the stored form of glucose (sugar). The prognosis of Muscular Phosphorylase Kinase Deficiency Disorder is good, since the condition is benign and may cause preventable symptoms in most cases. Phosphorylase kinase (PhK) deficiency causing glycogen storage disease type IX (GSD IX) results from deficiency of the enzyme phosphorylase b kinase, which has a major regulatory role in the breakdown of glycogen. Several tissue-specific isoforms of phosphorylase are noted. Urine studies are required only if rhabdomyolysis is suspected. The PYGM gene encodes the muscle isoform of glycogen phosphorylase (), which catalyzes and regulates the breakdown of glycogen to glucose-1-phosphate during glycogenolysis.This metabolic pathway is necessary for the generation of ATP during physical activity (Gautron et al., 1987). By all means, yes, the lysosome is inside the cytosol, but I’m just making a point that for whatever reason the USMLE is known to ask this weird point of differentiation. …deficiency of the liver enzyme glycogen phosphorylase, which governs the metabolic breakdown of glycogen to the simple sugar glucose, which can then be used to meet the body’s energy needs. As mentioned above, glycogen is a branched polymer. Terms of Use | State Fundraising Notices. This disease is one of a group of metabolic muscle diseases that interferes with the processing of food (in this case, carbohydrates) for energy production. Phosphorylase b kinase can also be assayed in leukocytes and erythrocytes. In some, the level is increased by multitudes - a person without GSD-V will have a CK between 60 and 400IU/L, while a person with the syndrome may have a level of 5,000 IU/L at rest, and may increase to 35,000 IU/L or more with muscle exertion. Patients may present at emergency rooms with severe fixed contractures of the muscles and often severe pain. Other articles where Phosphorylase is discussed: McArdle disease: …deficiency of the enzyme glycogen phosphorylase in muscle cells. Term UI T750954 Date 05/12/2009 Abbreviation: QA: LexicalTag NON ThesaurusID . Cells form glucose-1-phosphate instead of glucose during glycogen breakdown because the polar, phosphorylated glucose cannot leave the cell membrane and so is marked for intracellular catabolism. McArdle disease, also termed 'glycogen storage disease type V', is a disorder of skeletal muscle carbohydrate metabolism caused by inherited deficiency of the muscle-specific isoform of glycogen phosphorylase (GP-MM). The liver isoform is deficient in individuals with glycogen … If rhabdomyolysis is suspected, serum myoglobin, creatine kinase, lactate dehydrogenase, electrolytes and renal function will be checked. The liver glycogen phosphorylase is an integral enzyme in glucose metabolism, catalyzing the rate limiting step of glycogenolysis, breaking down glycogen into individual glucose-1-phosphate monomers. Myophosphorylase is the form of the glycogen phosphorylase found in muscle that catalyses the following reaction:[10][11][12], ((1→4)-alpha-D-glucosyl) (n) + phosphate = ((1→4)-alpha-D-glucosyl) (n-1) + alpha-D-glucose 1-phosphate. The enzyme’s absence causes glycogen to accumulate, greatly enlarging the liver and producing moderate hypoglycemia (low blood sugar), since the… Glycogen Synthase Deficiency Glycogen Phosphorylase Deficiency Glycogen Storage Disease Rate Limiting Enzyme Biochemistry. Left untreated, this can be life-threatening. Also modulates: Acid maltase deficiency phenotypes. By this mechanism, epinephrine induces the breakdown of muscle glycogen to supply muscle cells with increased glucose as a ready source of energy to respond to an extant acute stress. 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