Glycogen storage disease type IV the gene but show no symptoms of the disease. It affects 1 in 800,000 individuals worldwide, with 3% of all Glycogen Storage Diseases being type IV. It is a result of the absence of the glycogen branching enzyme, which is critical in the production of glycogen. This leads to very long unbranched glucose chains being stored in glycogen. The long unbranched molecules have a low solubility which leads to glycogen precipitation in the liver. These deposits subsequently build up in the body tissue, especially the heart and liver. The inability to breakdown glycogen in muscle cells causes muscle weakness. The
Glycogen debranching enzyme a glycogen branch down to four glucose residues, it will not remove further residues. Glycogen debranching enzymes assist phosphorylase, the primary enzyme involved in glycogen breakdown, mobilize glycogen stores. Phosphorylase can only cleave α-1,4- glycosidic bond between adjacent glucose molecules in glycogen but branches exist as α-1,6 linkages. When phosphorylase reaches four residues from a branching point it stops cleaving; because 1 in 10 residues is branched, cleavage by phosphorylase alone would not be sufficient in mobilizing glycogen stores. Before phosphorylase can resume catabolism, debranching enzymes perform two functions: Thus the debranching enzymes, transferase and α-1,6- glucosidase converts the branched