Glycogen configuration

Cellulose, a fibrous, tough, water-insoluble substance, is found in the cell walls of plants, particularly in stalks, stems, trunks, and all the woody portions of the plant body. Cellulose constitutes much of the mass of wood, and cotton is almost pure cellulose. Like amylose and the main chains of amylopectin and glycogen, the cellulose molecule is a linear, unbranched homopolysaccharide, consisting of 10,000 to 15,000 D-glucose units. But there is a very important difference in cellulose the glucose residues have the /3 configuration (Fig. 7-16),... 

The Configurations of Glycogen and Cellulose Dictate Their Roles... 

Cellulose, the major component of plant cell walls, is also a homopolymer of glucose. However, the glycosidic linkages in cellulose are in the /3 configuration instead of the a configuration, as in starch and glycogen. 

The reaction catalyzed by phosphorylase. An oxygen of a phosphate ion attacks C-1 of the terminal glucosyl unit of starch or glycogen, displacing the macromolecule and generating glucose-1-phosphate. The reaction proceeds with retention of configuration, a fact... 

Pyridoxal 5 -phosphate (PLP) was noticed to be a constituent of rabbit muscle phosphorylase in 1957, and since that time it has been shown that all a-glucan phosphorylases which give phosphorolysis products with retention of configuration contain PLP. The exact role of the PLP is still not known, though it has been shown that these a-glucan phosphorylases have an absolute requirement for PLP and that the Schiflfbase formed between PLP and glycogen phosphorylase can be reduced with borohydride without eliminating the catalytic activity of the enzyme. The P n.m.r. spectrum of PLP bound to phosphorylase b shows that deprotonation of the 5 -... 

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