DXS

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The DXS reaction (EC 2.2.1.7)

$Pyruvate + G3P \rightleftharpoons DXP + CO2$

Deoxyxylulose-5-phosphate synthase (DXS) catalyses the production of 1-deoxy-D-xylulose 5-phosphate (DXP) from pyruvate and glyceraldehyde 3-phosphate (G3P). This reaction is the first step in the MEP pathway.

Modelling DXS

In the kinetic model, the DXS reaction is modelled with reversible Michaelis-Menten using the Hanekom bi-bi random order generic equation. In total, this reaction requires five kinetic parameters (Kms for all substrates and products, and a forward Kcat) and one thermodynamic parameter (Equilibrium constant, Keq).

$V_\mathrm{DXS}= \cfrac{Kcat_\mathrm{forward} \bullet [DXS] \bullet \left( \cfrac{[Pyr]}{Km_\mathrm{DXS}} \right) \bullet \left( \cfrac{[G3P]}{Km_\mathrm{g3p}} \right) \bullet \left( 1 - \cfrac{\left( \cfrac{[DXP]\bullet[CO2]}{[Pyr]\bullet[G3P]} \right)}{K_\mathrm{eq}} \right)} {\left( 1 + \cfrac {[Pyr]}{Km_\mathrm{pyr}} + \cfrac{[CO2]}{Km_\mathrm{co2}}\right) \bullet \left( 1 + \cfrac{[G3P]}{Km_\mathrm{g3p}} + \cfrac{[DXP]}{KM_\mathrm{dxp}} \right)}$