Hexose-6-phosphate isomerase
The enzyme Hexose-6-phosphate isomerase converts Glucose 6-phosphate (Glc6P) into its isomer Fructose 6-phosphate (Fru6P). Isomers have the same molecular formula, but the atoms of each molecule are arranged differently.
Contents
Chemical reaction
![Glc6P \rightleftharpoons Fru6P](/wiki/images/math/b/1/4/b14645d59b3d0fb5d71b606423689d03.png)
Rate equation
Reversible competitive inhibition with Ery4P, 6PG and FBP. [1]
![v=\frac{V_{mf}\frac{[Glc6P]}{Km_{Glc6P}} - V_{mr} \frac{[Fru6P]}{Km_{Fru6P}} }{ 1 + \frac{[Glc6P]}{Km_{Glc6P}} + \frac{[Fru6P]}{Km_{Fru6P}} + \frac{[ERY4P]}{Ki_{ERY4P}} + \frac{[6PG]}{Ki_{6PG}} + \frac{[Fru1,6BP]}{Ki_{Fru1,6BP}} }](/wiki/images/math/4/f/d/4fd18a682ee7d511c57c5db14dc09b43.png)
Substituting with Haldane equation to ensure thermodynamic consistency we have
![v= \frac{V_{mf}\frac{[Glc6P]}{Km_{Glc6P}}\left(1 - \frac{[Fru6P]}{K_{eq}[Glc6P]} \right)}{ 1 + \frac{[Glc6P]}{Km_{Glc6P}} + \frac{[Fru6P]}{Km_{Fru6P}} + \frac{[ERY4P]}{Ki_{ERY4P}} + \frac{[6PG]}{Ki_{6PG}} + \frac{[Fru1,6BP]}{Ki_{Fru1,6BP}} }](/wiki/images/math/d/0/d/d0dd6e9a5e0114020d8f8122d107db36.png)
Parameter values
Parameter | Value | Units | Organism | Remarks |
---|---|---|---|---|
![]() |
0.4 [1] | ![]() |
HeLa cell line | 3 cell assays |
![]() |
0.9[1] | ![]() |
1 cell assay | |
![]() |
0.4 ![]() |
mM | 3 cell assays | |
![]() |
0.05[1] | mM | 2 cell assays | |
![]() |
0.001[1] | mM | Adjusted in the interval based on activity | |
![]() |
0.06[1] | mM | Adjusted in the interval based on activity | |
![]() |
0.015[1] | mM | Adjusted in the interval based on activity |
Parameters with uncertainty
- The V is measured in the reverse order for the enzyme (
) in [2] as
. The
is calculated based on Haldane equation. The same relative percent error for
is used to define the uncertainty of this parameter. The value is
. In the supplement of [1] the value is reported as 1.2
. Same error ratio for
reported in Cite error: Closing
</ref>
missing for<ref>
tag.
- The value of
,
and
are the averaged from the forward and reverse reaction value listed in Table S6 [1].
- The uncertainty for
in HeLa cell line is mentioned in the forward reaction as
and in the reverse direction as
. The mean value is calcualated as
and the standard deviation is calculated based on the same ratio mentioned in forward reaction which comes as
in mM.
- Same principle is used for
. The mean value is
and the standard deviation is calculted based on the same ratio of reverse reaction for HeLa cell line; 0.0043
- There are two reported value for
; 0.1[3], 0.06[1]. The mean and standard deviation are calcualted from these two values.
Parameter | Value | Units |
---|---|---|
![]() |
![]() |
![]() |
![]() |
Failed to parse (Cannot store math image on filesystem.): 195 \pm 110.5 | ![]() |
![]() |
![]() |
mM |
![]() |
![]() |
mM |
![]() |
![]() |
mM |
![]() |
![]() |
mM |
![]() |
![]() |
mM |
Equilibrium constant
Equilibrium constant | Conditions | Source |
---|---|---|
0.50 | pH=7, T=25°C | Lehninger, (2008)[4] p 553:
|
0.51 | pH=7, T=25°C | Lehninger, (1975)[5] p 396: Keq(reverse)=1.97 => Keq(forward)=1/1.97=0.51. |
0.41 | pH=7, T=25°C | Voet et al.[6] from Newshole et al. (1973) [7]p 97:
|
- Averaging these values gives
Refences
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Marín-Hernández A, Gallardo-Pérez JC, Rodríguez-Enríquez S et. al. (2011). Modeling cancer glycolysis. Biochim Biophys Acta 1807:755–767 (doi) Cite error: Invalid
<ref>
tag; name "Hernandez2011" defined multiple times with different content Cite error: Invalid<ref>
tag; name "Hernandez2011" defined multiple times with different content Cite error: Invalid<ref>
tag; name "Hernandez2011" defined multiple times with different content - ↑ Marín-Hernández A , Rodríguez-Enríquez S, Vital-González P A, et al. (2006). Determining and understanding the control of glycolysis in fast-growth tumor cells. Flux control by an over-expressed but strongly product-inhibited hexokinase. FEBS J., 273 , pp. 1975–1988(doi)
- ↑ Marin-Hernandez, A., Gallardo-Perez, J. C., Ralph, S. J., Rodriguez-Enriquez, S. & Moreno-Sanchez, R. (2009), HIF-1α modulates energy metabolism in cancer cells by inducing over-expression of specific glycolytic isoforms. Mini-Rev. Med. Chem. 9, 1084–1101
- ↑ David L. Nelson, Michael M. Cox (2008), Lehninger Principles of Biochemistry (5th edn), W. H. Freeman and Company
- ↑ Lehninger, A.L. (1975) Biochemistry (2nd edn), Worth
- ↑ Voet, D., Voet., J.G. and Pratt, C. W. (1999) Fundamentals of biochemistry, Wiley
- ↑ Newshole, E.A. and Stuart, C. (1973) Regulation in Metabolism, Wiley