Glycogen phosphorylase branching enzyme

Liver glycogen is synthesized from D-glucose in vivo by the enzyme system hexokinase-phosphoglucomutase-phosphorylase-branching enzyme (see Fig. 3). Glycogen is also formed from D-galactose and D-mannose... 

Intracellular Distribution of the Glycolytic and Glycogenolytic Enzymes Glycogen Synthesis 20 Role of Phosphorylase Other Pathways for Glycogen Synthesis Branching Enzyme... 

Debranching enzyme deconstructs the branches in glycogen that have been exposed by glycogen phosphorylase. The two-step process by which this occurs is diagrammed in Figure 1-14-4. Debranching enzyme ... 

Recently, the in vitro synthesis of amylopectin- or glycogen-like structures via a tandem reaction of phosphorylase and branching enzyme was reported [197-201]. 

Branching enzyme is responsible for the a-1,6-branching of the a-1,4-chain in the synthesis of glycogen. Branching enzyme enhances the rate of polysaccharide (endogenous glycogen) synthesis from glucose-1 -phosphate by phosphorylase. 

FIGURE 15-3 Removal of a terminal glucose residue from the nonreducing end of a glycogen chain by glycogen phosphorylase. This process is repetitive the enzyme removes successive glucose residues until it reaches the fourth glucose unit from a branch point (see Fig. 15-4). 

Glycogen phosphorylase and glycogen synthase alone are insufficient to synthesize and degrade glycogen. Synthesis also requires the action of the branching enzyme amylo-(l,4 —> 1,6-transglycosylase,97... 

The variation in degree of branching of these glycogens probably reflects differences in the relative activity of phosphorylase and branching enzyme during glycogen synthesis. 

For the synthesis of glycogen-type polysaccharides from a-n-glucopyran-osyl phosphate, two enzymes are required. Phosphorylases, in presence of a suitable primer, synthesize linear chains of -( —> 4)-linked n-glucose residues these are then converted into a branched polysaccharide by a branching enzyme. ... 

Glycogen phosphorylase sequentially removes the glu-cosyl residues from a glycogen branch until further action is sterically hindered by a branch point. This occurs when the branch is four residues long from the branch point. Debranching enzyme, a multifunctional protein, first removes the trisaccharide stump on the branch and then removes the branch point itself. The a(l 4) glycosidic bond link-... 

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