CHEM 445 / BIOL 445
Biochemistry II

J. D. Cronk
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16. header

Lecture 16. Glycogen structure and metabolism

Monday 26 February 2007

Introduction to glycogen metabolism. Glycogen structure and metabolism. Glycogen phosphorylase ("phosphorylase") and its PLP-mediated phosphorolysis mechanism. Transferase reactions involving phosphoryl groups and phosphate. Glycogen breakdown to glucose 1-phosphate is assisted by a transferase and an a-[1,6] glycosidase.

Reading: BTS6, Ch.21, pp.592-598.

  
16. Summary

Lecture 16 Summary

Introduction to glycogen metabolism. Glycogen structure and metabolism. Glycogen phosphorylase ("phosphorylase") and its PLP-mediated phosphorolysis mechanism. Glycogen breakdown to glucose 1-phosphate is assisted by a transferase and an a-[1,6] glycosidase.
Diagram of pathways connected to glucose 6-phosphate

Enzymes of glycogen metabolism

Glycogen phosphorylase ["phosphorylase", EC 2.4.1.1], phosphoglucomutase [EC 5.4.2.2 ]. Phosphorylase kinase [EC 2.7.11.19]

Glycogen structure

Glycogen is a highly-branched polymer.

Phosphorolysis and the mechanism of glycogen phosphorylase

 

Study questions

  • Explain why the body synthesizes glycogen.
  • Glycogen is a highly-branched polymer. What determines the extent of branching and the length of each branch?
  • Explain the energetic advantage of phosphorolysis of the a-[1,4] glycosidic bonds of glycogen chains over hydrolysis of these bonds.

Page updated 12-27-06

References

(References for glycogen, glycogen metabolism, phosphorylase mechanism)

1. Berg, Tymoczko, and Stryer. Biochemistry (BTS): 6th edition (2007, Freeman) Ch.21, pp.592-598.
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