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Essays in Biochemistry 



a mixture of glucose- 1 -phosphate and glucose as the sole products, free 

 glucose presumably arising uniquely from the hydrolysis of a-1,6' 

 bonds. The ratio of these products was therefore taken as equal to 

 the ratio of 1,4' to 1,6' links and the abundance of free glucose as a 

 measure of the number of branch points. 9 By the alternating attack 



R, reducing end of molecule. 



O, ©, and Q, glucose residues removed by first, second, and third degradation with phosphorylasc, 



respectively. 

 #, glucose residues split off as free glucose by amylo-l,6-glucosidase. 



Fig. 1. The structure of glycogen (from J. Larner, B. IUingworth, CJ. T. Cori, 

 and C. F. Cori, J. Biol. Chem., 199, 641, 1952). 



upon glycogen by phosphorylase and amyloglucnsidase, a series of limit 

 dextrins could be secured differing one from another by the successive 

 elimination of tiers of glucosidic residues. Regardless of whether gly- 

 cogen or a susceptible limit detrin thereof served as precursor, the 

 product secured after each treatment with phosphorylase represented 

 a loss of 35-45% of the glucosidic residues initially present. 10 A 

 schematic representation of what was happening is shown in Fig. 1, 

 from which it will be seen that the alternating exposure to phospho- 

 rylase and amyloglucosidase has resulted in the peeling of the molecule, 

 removal of successive peripheral layers, much as an onion might be 

 peeled. 



