| | Molecule Name/
Site Name | Km (uM) | kcat (1/s) | Ratio
(k2/k3) | Enzyme Type | Substrate | Product |
| 1 |
Enzyme Activity:
CaM-GEF-act-ras
Enzyme Molecule:
CaM-GEF | 0.505051 | 0.02 | 4 | explicit E-S complex | GDP-Ras
| GTP-Ras
|
| | Kinetics same as GEF-bg_act-ras |
| 2 |
Enzyme Activity:
GAP-inact-ras
Enzyme Molecule:
GAP | 1.0104 | 10 | 100 | explicit E-S complex | GTP-Ras
| GDP-Ras
|
| | From Eccleston et al JBC 268(36)pp27012-19 get Kd < 2uM, kcat - 10/sec From Martin et al Cell 63 843-849 1990 get Kd ~ 250 nM, kcat = 20/min I will go with the Eccleston figures as there are good error bars (10%). The two sets of values are reasonably close. k1 = 1.666e-3/sec, k2 = 1000/sec, k3 = 10/sec (note k3 is rate-limiting) This is one of the rare cases where we have direct info on the k3 being rate-limiting. Hence the ratio I use for the k2:k3 rates is 100 rather than the usual 4. |
| 3 |
Enzyme Activity:
GEF*-act-ras
Enzyme Molecule:
GEF* | 0.505051 | 0.02 | 4 | explicit E-S complex | GDP-Ras
| GTP-Ras
|
| | Kinetics from Orita et al JBC 268(34):25542-25546. Note that the Vmax is slow, but it does match the slow GTP hydrolysis rates. |
| 4 |
Enzyme Activity:
GEF-bg_act-ras
Enzyme Molecule:
GEF-Gprot-bg | 0.505051 | 0.02 | 4 | explicit E-S complex | GDP-Ras
| GTP-Ras
|
| | Kinetics based on the activation of Gq by the receptor complex in the Gq model (in turn based on the Mahama and Linderman model) k1 = 2e-5, k2 = 1e-10, k3 = 10 (I do not know why they even bother with k2). Lets put k1 at 2e-6 to get a reasonable equilibrium More specific values from, eg.g: Orita et al JBC 268(34) 25542-25546 from rasGRF and smgGDS: k1=3.3e-7; k2 = 0.08, k3 = 0.02 |
