MEK-Activation(BRaf)

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Binding Reaction

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

Kinetic Equation

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

final Parameter

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

$K_{\text{m}}(\text{Mek}) = 0.275\; \pm\; 0.667398 \cdot 1.5\; \mu M = 0.275\; \pm\; 1.001096\; \mu M$

Parameter Reference

Parameter Calculation

Reference

kcat: The values are averaged and then divided by 60 s to change the unit. $k_{cat} = \frac{\frac{15.4 + 14.7}{2}}{60\; s \cdot \mu M}\; \pm\; = 0.25083\; \frac{1}{s}$ $\sigma_{k_{cat}} = \frac{1}{2} \cdot (\frac{0.7}{15.4} + \frac{1.2}{14.7})\cdot 0.25083\; \frac{1}{s} = 0.0159386\; \frac{1}{s}$ Km: The two measured Km values are also averaged. $K_m = \frac{0.19+0.36}{2}\; \mu M = 0.275\; \mu M$ $\sigma_{K_m} = \frac{1}{2} \cdot (\frac{0.05}{0.19} + \frac{0.08}{0.36})\cdot 0.275\; \mu M = 0.667398\; \mu M$ 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.

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 to but slightly smaller 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 0.95 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.