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Enzyme List for pathway Ras (Pathway Number 37)

 Molecule Name/
Site Name 		Km (uM) kcat (1/s)Ratio
(k2/k3)		Enzyme TypeSubstrate Product
1 Enzyme Activity:
GAP-inact-ras

Enzyme Molecule:
GAP		1.010410100explicit E-S complexGTP-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.
2 Enzyme Activity:
GEF*-act-ras

Enzyme Molecule:
GEF*		0.50510.024explicit E-S complexGDP-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.
Pathway DetailMolecule ListEnzyme ListReaction List