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Reaction Name | Pathway Name / Pathway No.![](database/fig/up.png) | Kf | Kb | Kd | tau | Reagents |
1 | bg-act-GEF | Ras
Pathway No. 76 | 6 (uM^-1 s^-1) | 1 (s^-1) | Kd(bf) = 0.1667(uM) | - | Substrate: BetaGamma inact-GEF
Products: GEF-Gprot-bg
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| SoS/GEF is present at 50 nM ie 3e4/cell. BetaGamma maxes out at 9e4. Assume we have 1/3 of the GEF active when the BetaGamma is 1.5e4. so 1e4 * kb = 2e4 * 1.5e4 * kf, so kf/kb = 3e-5. The rate of this equil should be reasonably fast, say 1/sec | 2 | dephosph-GEF | Ras
Pathway No. 76 | 1 (s^-1) | 0 (s^-1) | - | - | Substrate: GEF*
Products: inact-GEF
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| This rate is based on the known ratio of GDP-Ras to GTP-Ras. Basal: Ras.GTP = 7% Stimulated 15% Time course is within 10 min, probably much faster as not all early data points are there. See Gibbs et al JBC 265(33):20437-20422 | 3 | Ras-intrinsic-GT Pase | Ras
Pathway No. 76 | 0.0001 (s^-1) | 0 (s^-1) | - | - | Substrate: GTP-Ras
Products: GDP-Ras
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| This is extremely slow (kf = 1e-4), but it is significant as so little GAP actually gets complexed with it that the total GTP turnover rises only by 2-3 X (see Gibbs et al, JBC 265(33) 20437-20422) and Eccleston et al JBC 268(36) 27012-27019 There is no back reaction as we assume this to be a regular irreversible Michaelis-Menten zeroth order hydrolysis. | 4 | dephosph-GAP | Ras
Pathway No. 76 | 0.1 (s^-1) | 0 (s^-1) | - | - | Substrate: GAP*
Products: GAP
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| Assume a reasonably good rate for dephosphorylating it, 0.1/sec. This fits well with resting levels of active kinase and the degree of activation as well as time-course of turnoff of Ras activation, but data is quite indirect. | 5 | CaM-bind-GEF | Ras
Pathway No. 76 | 60 (uM^-1 s^-1) | 1 (s^-1) | Kd(bf) = 0.0167(uM) | - | Substrate: inact-GEF CaM-Ca4
Products: CaM-GEF
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| We have no numbers for this. It is probably between the two extremes represented by the CaMKII phosph states, and I have used guesses based on this. kf=1e-4 kb=1 The reaction is based on Farnsworth et al Nature 376 524-527 1995 | 6 | dephosph-inact-G EF* | Ras
Pathway No. 76 | 1 (s^-1) | 0 (s^-1) | - | - | Substrate: inact-GEF*
Products: inact-GEF
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