Difference between revisions of "UDPG-pyrophosphorylase"

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[[Category:Uncertainty]]
 
This enzyme converts UTP and G1P to UDP-glucose (UDPG) and pyrophosphate (PPi)
 
This enzyme converts UTP and G1P to UDP-glucose (UDPG) and pyrophosphate (PPi)
  
 
==Chemical equation==
 
==Chemical equation==
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<center><math> UTP + Glc1P \rightarrow UDPG + PPi</math></center>
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<center><math> UTP + Glc1P \leftrightarrow UDPG + PPi</math></center>
  
 
==Rate equation==
 
==Rate equation==
−
Reversible Bi substrate Michaelis-Menten equation with random binding order is used
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Reversible Bi substrate Michaelis-Menten equation with random binding order is used <ref name="Palm_thesis_2013> Palm, D.C. (2013). ''The regulatory design of glycogen metabolism in mammalian skeletal muscle'' (Ph.D.). University of Stellenbosch</ref>
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<center><math> \frac{ \frac{V_{max}}{K_{UTP}K_{Glc1P}} \left( [UTP][Glc1P] - \frac{[UDPG][PPi]}{K_{eq}} \right)  }{ \left( 1 + \frac{[UTP]}{K_{UTP}} + \frac{[PPi]}{K_{PP_{i}}} \right) \left( 1 + \frac{[UDPG]}{K_{UDPG}} + \frac{[Glc1P]}{K_{Glc1P}} \right)  } </math></center>
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<center><math> \frac{ \frac{V_{max}}{K_{UTP}K_{Glc1P}} \left( [UTP][Glc1P] - \frac{[UDPG][PPi]}{K_{eq}} \right)  }{ \left( 1 + \frac{[UTP]}{K_{UTP}} + \frac{[PPi]}{K_{PPi}} \right) \left( 1 + \frac{[UDPG]}{K_{UDPG}} + \frac{[Glc1P]}{K_{Glc1P}} \right)  } </math></center>
  
 
==Parameter values==
 
==Parameter values==
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{|class="wikitable"
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! Parameter
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! Value
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! Units
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! Organism
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! Remarks
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|-
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|<math>V_{max}</math>
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|200 <ref name = "villar_1960"> Villar-Palasi C & Larner J (1960). ''Levels of activity of the enzymes of the glycogen cycle in rat tissues''. Arch Biochem Biophys 86, 270–273.</ref>
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|<math>min^{-1}</math>
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|rowspan="6"|Recombinant, human muscle
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|rowspan="6"|
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|-
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|<math>K_{Glc1P}</math>
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|0.4 <ref name="duggleby_1996"> Duggleby RG, Chao YC, Huang JG, Peng HL & Chang HY (1996). ''Sequence differences between human muscle and liver cDNAs for UDPglucose pyrophosphorylase and kinetic properties of the recombinant enzymes expressed in Escherichia coli''. Eur J Biochem 235, 173–179. </ref>
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|mM
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|-
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|<math>K_{UTP}</math>
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|0.92 <ref name="duggleby_1996"></ref>
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|mM
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|-
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|<math>K_{UDPG}</math>
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|<math> 6.3 \times 10^{-2} </math> <ref name="duggleby_1996"></ref>
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|mM
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|-
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|<math>K_{ppi}</math>
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|<math>0.38</math><ref name="duggleby_1996"></ref>
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|mM
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|-
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|<math>K_{eq}</math>
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|<math>0.24</math><ref name="Bergamini_1983">Bergamini C, Signorini M, Ferrari C & Dallocchio F (1983), ''Non-Michaelian kinetics of rabbit muscle uridine diphosphoglucose pyrophosphorylase'', Arch Biochem Biophys 227, 397–405</ref>
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|Dimensionless
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|}
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 +
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==Parameters with uncertainty==
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* The value of <math>V_{max}</math> is reported to be <math>9.6 %</math> of <math>V_{max, PGLM}</math>. The Std. Dev. for <math>V_{max, PGLM}</math> was considered to be <math>10.5%</math> of its mean value. Same error percentage is considered for <math>V_{max}</math>.
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{|class="wikitable"
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! Parameter
 +
! Value
 +
! Units
 +
! Organism
 +
! Remarks
 +
|-
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|<math>V_{max}</math>
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|<math>200 \pm 21</math> <ref name = "villar_1960"> Villar-Palasi C & Larner J (1960). ''Levels of activity of the enzymes of the glycogen cycle in rat tissues''. Arch Biochem Biophys 86, 270–273.</ref>
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|<math>mM min^{-1}</math>
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|rowspan="6"|Recombinant, human muscle
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|rowspan="6"|
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|-
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|<math>K_{Glc1P}</math>
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|<math> 0.4 \pm 0.051 </math> <ref name="duggleby_1996"> Duggleby RG, Chao YC, Huang JG, Peng HL & Chang HY (1996). ''Sequence differences between human muscle and liver cDNAs for UDPglucose pyrophosphorylase and kinetic properties of the recombinant enzymes expressed in Escherichia coli''. Eur J Biochem 235, 173–179. </ref>
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|mM
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|-
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|<math>K_{UTP}</math>
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|<math>0.97 \pm 0.08</math> <ref name="duggleby_1996"></ref>
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|mM
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|-
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|<math>K_{UDPG}</math>
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|<math> 0.063 \pm 0.006 </math> <ref name="duggleby_1996"></ref>
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|mM
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|-
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|<math>K_{ppi}</math>
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|<math>0.38 \pm 0.036</math><ref name="duggleby_1996"></ref>
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|mM
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|-
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|<math>K_{eq}</math>
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|<math>0.20 \pm 0.08</math>
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|Dimensionless
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|}
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=== Equilibrium constant ===
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{| class="wikitable"
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! Equilibrium constant
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! Conditions
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! Source
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|-
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| <math>0.20 \pm 0.08</math>
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| pH=7 and 7.9, T=25°C, 10mM Mg2+
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| NIST database "Thermodynamics of Enzyme-Catalyzed Reactions" entry [[http://xpdb.nist.gov/enzyme_thermodynamics/enzyme_data1.pl?T1=58TUR/TUR_684]] from Atkinson et al. (1958) <ref name="Turner">Turner, D.H.; Turner, J.F.; Biochem. J.; 69, 448 (1958)</ref> reported 4 values for Keq; 0.119, 0.286, 0.139, 0.263. Taking mean and std. for these values give <math>K_{eq} = 0.20 \pm 0.08 </math>(n=4).
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|}
  
 
==References==
 
==References==
 +
<references/>

Latest revision as of 14:42, 22 September 2014

This enzyme converts UTP and G1P to UDP-glucose (UDPG) and pyrophosphate (PPi)

Chemical equation

UTP + Glc1P \leftrightarrow UDPG + PPi

Rate equation

Reversible Bi substrate Michaelis-Menten equation with random binding order is used [1]

\frac{ \frac{V_{max}}{K_{UTP}K_{Glc1P}} \left( [UTP][Glc1P] - \frac{[UDPG][PPi]}{K_{eq}} \right) }{ \left( 1 + \frac{[UTP]}{K_{UTP}} + \frac{[PPi]}{K_{PPi}} \right) \left( 1 + \frac{[UDPG]}{K_{UDPG}} + \frac{[Glc1P]}{K_{Glc1P}} \right) }

Parameter values

Parameter Value Units Organism Remarks
V_{max} 200 [2] min^{-1} Recombinant, human muscle
K_{Glc1P} 0.4 [3] mM
K_{UTP} 0.92 [3] mM
K_{UDPG} 6.3 \times 10^{-2} [3] mM
K_{ppi} 0.38[3] mM
K_{eq} 0.24[4] Dimensionless


Parameters with uncertainty

  • The value of V_{max} is reported to be 9.6 % of V_{max, PGLM}. The Std. Dev. for V_{max, PGLM} was considered to be 10.5% of its mean value. Same error percentage is considered for V_{max}.
Parameter Value Units Organism Remarks
V_{max} 200 \pm 21 [2] mM min^{-1} Recombinant, human muscle
K_{Glc1P} 0.4 \pm 0.051 [3] mM
K_{UTP} 0.97 \pm 0.08 [3] mM
K_{UDPG} 0.063 \pm 0.006 [3] mM
K_{ppi} 0.38 \pm 0.036[3] mM
K_{eq} 0.20 \pm 0.08 Dimensionless

Equilibrium constant

Equilibrium constant Conditions Source
0.20 \pm 0.08 pH=7 and 7.9, T=25°C, 10mM Mg2+ NIST database "Thermodynamics of Enzyme-Catalyzed Reactions" entry [[1]] from Atkinson et al. (1958) [5] reported 4 values for Keq; 0.119, 0.286, 0.139, 0.263. Taking mean and std. for these values give K_{eq} = 0.20 \pm 0.08 (n=4).

References

  1. ↑ Palm, D.C. (2013). The regulatory design of glycogen metabolism in mammalian skeletal muscle (Ph.D.). University of Stellenbosch
  2. ↑ 2.0 2.1 Villar-Palasi C & Larner J (1960). Levels of activity of the enzymes of the glycogen cycle in rat tissues. Arch Biochem Biophys 86, 270–273.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Duggleby RG, Chao YC, Huang JG, Peng HL & Chang HY (1996). Sequence differences between human muscle and liver cDNAs for UDPglucose pyrophosphorylase and kinetic properties of the recombinant enzymes expressed in Escherichia coli. Eur J Biochem 235, 173–179.
  4. ↑ Bergamini C, Signorini M, Ferrari C & Dallocchio F (1983), Non-Michaelian kinetics of rabbit muscle uridine diphosphoglucose pyrophosphorylase, Arch Biochem Biophys 227, 397–405
  5. ↑ Turner, D.H.; Turner, J.F.; Biochem. J.; 69, 448 (1958)
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