Debranching enzyme deficiency

In glycogenosis type III (debranching enzyme deficiency) the absorption maximum is around 410 nm in muscle in liver the maximum remains around 460 nm, but there is a pronounced shoulder at 410 nm. In glycogenosis type IV (branching enzyme deficiency) the absorption maximum is around 530 nm. 

Pan, D., and Nelson, O. E. 1984. A debranching enzyme deficiency in endosperms of the sugary 1 mutants of maize. Plant PhysioL 74,324-328. 

Glycogen Storage Disease Type III Debranching Enzyme Deficiency. 304... 

Slonim AE, Coleman RA, Moses WS. Myopathy and growth failure in debrancher enzyme deficiency improvement with high-protein nocturnal enteral therapy. J Pediatr. 1984 105(6) 906-11. 

Table 15.10. Glycogen storage disease type 3 (debrancher enzyme deficiency) ...

A debranching enzyme called isoamylase is involved in synthesis of the starch granule and its polysaccharide components (34-37). Mutant plants deficient in isoamylase activity accumulate a soluble a-glucan designated phytoglycogen (3, 37, 38) and little starch. 

GSD type III, Cori s disease Deficiency of debranching enzyme activity causes accumulation of limit dextrins. See text. 

To explain the variation in the phosphate content of starches, it is postulated that some plants contain a specific phosphatase such an enzyme would have to possess unusual powers of penetration, since R-en-zyme, for example, cannot attack the interior of an amylopectin molecule. Moreover, a considerable proportion of the phosphorus would be situated in outer chains there is no evidence for this. (5) The formation of waxy-type starches is attributed to a low activity of the debranching enzyme caused by the presence of an inhibitor(s) to the debranching mechanism or by a deficiency of the debranching enzyme. Waxy-type starches should, therefore, contain a higher degree of branching than that actually observed (about 5%). 

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