Liver phosphorylase kinase deficiency

D-l) Liver phosphorylase kinase deficiency (Type Vm GSD). The defect in this enzyme prevents activation of liver phosphorylase (see fig. 3.2). There is accumulation of glycogen in the liver and liver enlargement. Diagnosis is made on assay for the defective enzyme in liver biopsy or in leukocytes or erythrocytes. 

Table 15.15. Glycogen storage disease type 9 (liver phosphorylase kinase deficiency) ...

Type VIII Deficiency of liver phosphorylase kinase As for type VI. 

In liver phosphorylase deficiency (glycogenosis type VI, Hers disease Fig. 42-1) and in two genetic forms of phosphorylase kinase deficiency, one of which is X-linked recessive, the other of which is autosomal recessive, hypoglycemia is either absent or mild. Symptoms of brain dysfunction do not usually occur (type VIII, Fig. 42-1) [1],... 

Type VI (Liver Phosphorylase or Phosphorylase Kinase Deficiency)... 

Glycogenosis type VIII (phosphorylase b kinase deficiency) gives rise to myopathy and liver disease, either singly or in combination. Phosphorylase b kinase (PBK) converts the inactive b form of both muscle and liver phosphorylases to the active a forms of the enzymes. The ischemic lactate test sometimes shows a flat result as in McArdle s disease, but is more likely to be normal. Histochemical demonstration of myophosphorylase activity in tissue sections shows a near-normal reaction due to the presence of phosphorylase a. Accumulation of glycogen is modest and found mainly in type 2 (fast-twitch glycolytic) muscle fibers. 

H21. Hug, G, Schubert, W. K., and Chuck, G., Deficient activity of dephospho-phosphorylase kinase and accumulation of glycogen in the liver, J. Clin. Invest. 48, 704-715 (1969). 

More recently a case was described [127] in which the total activity of phosphorylase in both muscle and liver was normal, but the enzyme was in the inactive form. Evidence was obtained for a deficiency of the cyclic 3, 5 -AMP-dependent kinase which phosphorylates phosphorylase kinase which, in turn, converts inactive phosphorylase b to active phosphorylase a. 

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