CHEM 445 / BIOL 445
Biochemistry II

J. D. Cronk
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17. header

Lecture 17. Glycogen metabolism: Regulation of phosphorylase.

Wednesday 28 February 2007

Regulaton of glycogen phosphorylase. Allosteric regulation of muscle and liver phosphorylase isozymes. Regulation of glycogen phosphorylase by phosphorylase kinase. Differences in regulatory properties between muscle and liver isoforms of phosphorylase. Control of phosphorylase activity by a hormone-triggered signal transduction pathway. Phosphorylase kinase and regulation of phosphorylase kinase by PKA and calcium

Reading: BTS6, Ch.21, pp.598-604.

  
17. Summary

Lecture 17 Summary

¶ Regulation of phosphorylase

Structural features of phosphorylase related to regulation. Phosphorylase a and phosphorylase b Allosteric regulation of phosphorylase of muscle and liver isozymes of phosphorylase.

¶ Phosphorylase kinase

Phosphorylase kinase subunit composition. Regulation of the regulator: Phosphorylase kinase is itself phosphorylated by PKA in response to a hormonal signal, and is regulated by calcium ion levels.

Regulation of glycogen breakdown

Glycogen phosphorylase ["phosphorylase", EC 2.4.1.1], phosphoglucomutase [EC 5.4.2.2 ]. Phosphorylase kinase [EC 2.7.1.38]

Kinases and phosphatases

Edwin Krebs and Edmond Fischer won the 1992 Nobel Prize for Physiology or Medicine for their discoveries of "reversible protein phosphorylation as a biological regulatory mechanism".

 

 

Study questions

  • Describe the signal transduction pathway based on intracellular cyclic AMP.

Page updated 12-27-06

References

1. Berg, Tymoczko, and Stryer. Biochemistry (BTS): 6th edition (2007, Freeman) Ch.21, pp.592-604.
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