The Fine Structure of Glycogen from Type IV Glycogen‐Storage Disease

Abstract

The structure of glycogen isolated from a male child suffering from type IV glycogenosis (amylopectinosis) has been examined. It is confirmed that the polysaccharide is superficially similar to plant amylopectin. However, a more searching analysis involving the examination and comparison of the pullulanase‐debranched polysaccharides, revealed marked differences between the profiles of unit chains that make up the macromolecules. The type IV glycogen contains a significant proportion of short branches. The occurrence of these branches is consistent with a recent hypothesis advanced to explain why a branched polysaccharide should be synthesized in the absence of branching enzyme, this being the enzyme deletion that characterizes this type of glycogenosis.

The Pathway of Exogenous and Endogenous Carbohydrate Utilization in Escherichia coli: A Dual Function for the Enzymes of the Maltose Operon

“…Even in three-day cultures, no growth was apparent with glycogen as carbon source. This inability to grow on glycogen reflects the essential inability of pullulanase to attack the polysaccharide [33].…”

A Modified Enzymatic Method for Measurement of Glycogen Content in Glycogen Storage Disease Type IV

“…But this procedure is not suitable for GSD IV glycogen measurement due to the heavy loss of insoluble glycogen during sample preparation. In this study, we described a modified method that includes an extra boiling step prior to centrifugation of tissue homogenates to dissolve the insoluble glycogen in GSD IV (Mercier and Whelan 1970). To determine the length of boiling time needed for complete glycogen dissolution, we quantified glycogen after boiling the homogenates (150-300 ml) 3, 5, 10, and 15 min and saw no difference among all the time points (data not shown).…”

“…In GSD III, loss of GDE enzyme activity hinders further breakdown of glycogen from branching points, resulting in the accumulation of abnormal glycogen with short outer chains (Chen et al 2009). In GSD IV, deficiency of GBE leads to the production of lessbranched and poorly soluble polysaccharides (polyglucosan bodies, PB) in all body tissues (Brown and Brown 1966;Fernandes and Huijing 1968;Mercier and Whelan 1970).…”

Further Characterization of Glycogen from Type‐IV Glycogen‐Storage Disease

“…I n a previous publication we used the amylopectin debranching enzyme, pullulanase, to show that the resemblance of type IV glycogen to amylopectin was superficial [3]. Pullulanase almost completely debranches plant amylopectin into its unit chains but has no action on human liver glycogen.…”

“…Furthermore, the enzyme liberated maltose, maltotriose and maltotetraose from the polysaccharide. None of these oligosaccharides comprises any significant part of the population of unit chains in normal glycogen and amylopectin [3].…”