MEK-Activation(Raf1)

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Binding Reaction

$\text{Mek} + \text{Raf1PP} \rightleftharpoons \text{MekPP} + \text{Raf1PP}$

Kinetic Equation

$v_{\text{Mek-Activation}} = \frac{k_{cat} \cdot [\text{Raf1PP}] \cdot [\text{Mek}] \cdot (1-\frac{[\text{MekPP}]}{[\text{Mek}] \cdot K_{eq}})}{Km_{\text{Mek}} \cdot (1 + \frac{[\text{Mek}]}{Km_{\text{Mek}}} + \frac{[\text{MekPP}]}{Km_{\text{MekPP}}})}$

final Parameter

$k_{\text{cat}} = 0.25083\; \pm\; 0.0159386 \cdot 1.5\; \frac{1}{s} = 0.25083\; \pm\; 0.0239079\; \frac{1}{s}$

$K_{m} = 0.8\; \mu M \pm 0.5348 \cdot 0.8\; \mu M = 0.8\; \mu M \pm 0.428\; \mu M$

Parameter Reference

Parameter Calculation

Reference

kcat: The values are averaged and then divided by 60 s to change the unit. $k_{cat} = \frac{\frac{15.4 + 14.7}{2}}{60\; s} = 0.25083\; \frac{1}{s}$ $\sigma_{k_{cat}} = \frac{1}{2} \cdot (\frac{0.7}{15.4} + \frac{1.2}{14.7})\cdot 0.25083\; \frac{1}{s} = 0.0159386\; \frac{1}{s}$ The so calculated error is increased by 1.5, because only a similar reaction is measured and so the uncertainty about the parameter is larger. Km: Force et al. measured a Km for c-Raf1: Km = 0.8 μM For the uncertainty estimation the averaged relative error is used.

Yong Jia et al. (2005) table 3

Km_P value and equilibrium constant

The K_m value for the product is assumed to be similar but slightly higher than the the K_m value of the substrate because of the similarity of the both species. Therefore the K_m value of the substrate is multiplied by 1.05 to gain the one of the product and the uncertainty is increased by increasing the error on Km_substrate by 50%.

For information about the equilibrium constant please see here.