Glycogen phosphorylase
Glycogen phosphorylase (GP) is a dimeric enzyme that catalyses the reaction in which the terminal glucose residue from a glycogen chain is phosphorylated and cleaved from the chain, releasing it as Glc1P.
Chemical equation
![Glycogen_{n+1} + Pi \rightleftharpoons Glycogen_{n} + Glc1P](/wiki/images/math/8/6/4/86402737c580a1f36c691d2a13dcbb43.png)
Rate equation
MWC model was used to formualte the rate law. [1]
![\frac{V_{max} \times n \times \frac{[Pi]}{K_{r,Pi}} \left( 1 + \frac{[Pi]}{K_{r,Pi}} + \frac{[Glc1P]}{K_{r,Glc1P}} \right)^{n-1} }{\left( 1 + \frac{[Pi]}{K_{r,Pi}} + \frac{[Glc1P]}{K_{r,Glc1P}} \right)^n + L_u \left( 1 + \frac{[Pi]}{K_{u,Pi}} + \frac{[Glc1P]}{K_{u,Glc1P}} \right)^n \left( \frac{1 + \frac{[Glc6P]}{K_{u,Glc6P}}}{1 + \frac{[AMP]}{K_{r,AMP}} + \frac{[Glc6P]}{K_{r,Glc6P}}} \right)^n } + \frac{V_{max} \times n \times \frac{[Pi]}{K_{r,Pi}} \left( 1 + \frac{[Pi]}{K_{r,Pi}} + \frac{[Glc1P]}{K_{r,Glc1P}} \right)^{n-1} }{\left( 1 + \frac{[Pi]}{K_{r,Pi}} + \frac{[Glc1P]}{K_{r,Glc1P}} \right)^n + L_t \left( 1 + \frac{[Pi]}{K_{t,Pi}} + \frac{[Glc1P]}{K_{t,Glc1P}} \right)^n \left( \frac{1 + \frac{[AMP]}{K_{t,AMP}} \frac{[Glc6P]}{K_{t,Glc6P}}}{1 + \frac{[AMP]}{K_{r,AMP}} + \frac{[Glc6P]}{K_{r,Glc6P}}} \right)^n \left( 1 + \frac{[ATP]}{K_{t,ATP}} \right)^n }](/wiki/images/math/7/e/5/7e599d4304d1f49ee3e3d2d32f556863.png)
An alternative rate equation without considering the allosteric regulation is given as
Parameter values
Parameter | Value | Units | Organism | Remarks |
---|---|---|---|---|
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2 | Dimensionless | Recombinant, human muscle | |
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50 | ![]() | ||
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2.08 | mM | ||
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4.32 | mM | ||
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41.53 | mM | ||
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0.67 | mM | ||
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82.02 | mM | ||
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27.92 | mM | ||
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mM | ||
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0.53 | mM | ||
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3.9 | mM | ||
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7.42 | mM | ||
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0.56 | mM | ||
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0.27 | mM | ||
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5.93 | Dimensionless | ||
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34741 | Dimensionless |
References
- ↑ Palm, D.C. (2013). The regulatory design of glycogen metabolism in mammalian skeletal muscle (Ph.D.). University of Stellenbosch