Difference between revisions of "Triosephosphate isomerase"

Revision as of 10:30, 29 May 2014

This enzyme rapidly inter-converts the molecules Dihydroxyacetone phosphate (DHAP) and Glyceraldehyde 3-phosphate (Gly3P). Gly3P is removed as soon as it is formed to be used in the next step of glycolysis.

DHAP \rightleftharpoons Gly3P

Reversible Michaelis-Menten is used ^[1]

v = \frac{ V_{mf}\frac{[DHAP]}{K_{DHAP}} - V_{mr}\frac{[Gly3P]}{K_{Gly3P}} }{1 + \frac{[DHAP]}{K_{DHAP}} + \frac{[Gly3P]}{K_{Gly3P}} }

Parameter	Value	Units	Organism
$V_{mf}$	5 ^[1]	$mM \times min^{-1}$	Hela cell line
$V_{mr}$	42^[2]	$mM \times min^{-1}$
$Km_{Gly3P}$	0.51^[1]	mM
$Km_{DHAP}$	1.6^[1]	mM

The activity is measured in Activity in the reverse reaction in Hernandez (2006) et. al. $V_{mf}$ is sampled based on Haldane equation $K_{eq} = \frac{V_{forward}*K_{product}}{V_{reverse}*K_{substrate}}$ using the value Failed to parse (Cannot store math image on filesystem.): K_{eq} = 20.9 \pm 3.1 , $Km_{Gly3P}$ and $Km_{DHAP}$ . Alternatively the reported fixed point value can be considered with the standard deviation calculated based on the same ratio of $V_{mf}$ which is $\approx 31%$ . This gives the value $V_{mf}=0.063 \pm 0.028$

Parameter	Value	Units	Organism
$V_{mf}$	Sampled based on the Haldane equation.	$mM \times min^{-1}$
$V_{mr}$	$42 \pm 13 (3)$ ^[2]	$mM \times min^{-1}$
$Km_{Gly3P}$	$0.40 \pm 0.03 (4)$ ^[3]	mM	Human liver
$Km_{DHAP}$	$0.59 \pm 0.01 (4)$ ^[3]	mM	Human liver
$K_{eq}$	Failed to parse (Cannot store math image on filesystem.): 20.9 \pm 3.1 (4) ^[3]	mM

↑ ^1.0 ^1.1 ^1.2 ^1.3 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
↑ ^2.0 ^2.1 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)
↑ ^3.0 ^3.1 ^3.2 Snyder, R.; Lee, E.W. (1975), Triosephosphate isomerase from human and horse liver,Methods Enzymol. 41B, 430-434

@@ Line 37: / Line 37: @@
 ==Parameters with uncertainty==
-* The activity is measured in Activity in the reverse reaction in Hernandez (2006) ''et. al.'' <math>V_{mf}</math> is sampled based on Haldane equation <math>K_{eq} = \frac{V_{forward}*K_{product}}{V_{reverse}*K_{substrate}}</math> using the value <math>K_{eq} = 20.9 \pm 3.1</math>, <math>Km_{Gly3P}</math> and <math>Km_{DHAP}</math>.
+* The activity is measured in Activity in the reverse reaction in Hernandez (2006) ''et. al.'' <math>V_{mf}</math> is sampled based on Haldane equation <math>K_{eq} = \frac{V_{forward}*K_{product}}{V_{reverse}*K_{substrate}}</math> using the value <math>K_{eq} = 20.9 \pm 3.1</math>, <math>Km_{Gly3P}</math> and <math>Km_{DHAP}</math>. '''Alternatively''' the reported fixed point value can be considered with the standard deviation calculated based on the same ratio of <math>V_{mf}</math> which is <math>\approx 31%</math>. This gives the value <math>V_{mf}=0.063 \pm 0.028 </math>
 {|class="wikitable"
 ! Parameter