Amylo-alpha-1, 6-glucosidase, 4-alpha-glucanotransferase
Glycogen debranching enzyme is involved in glycogen degradation and has two independent catalytic activities: a 4-alpha-glucotransferase activity (EC 220.127.116.11) and a amylo-1,6-glucosidase activity (EC 18.104.22.168). Both activities occur at different sites on the single polypeptide chain. Mutations in this gene cause glycogen storage disease. A wide range of clinical and enzymatic variability occurs in glycogen debrancher deficiency, some of which may be due to tissue-specific alternative splicing. Six splice varients that differ in the 5' end have been identified in liver and muscle tissue. Variants 1, 5, and 6 are present in both liver and muscle, whereas variants 2, 3, and 4 occur in muscle. Variants 1 through 4 encode identical proteins (isoform 1) that include 27 N-terminal amino acids not found in splice variants 5 and 6. Variants 5 and 6 encode different amino-terminal ends of 10 and 11 amino acids in protein isoforms 2 and 3, respectively, with the remainder of the peptide identical to that of isoforms 1.