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Accession Type:
Network
MAPK_network_
2003
Shared_Object_
MAPK_network_
2003
PKC
PLA2
PLCbeta
Gq
MAPK
Ras
EGFR
Sos
PLC_g
CaMKII
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 Reaction
CaM
PP1
PP2B
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Reaction List for pathway CaMKII (Pathway Number 216)

Kd is calculated only for second order reactions, like nA+nB <->nC or nA<->nC+nD, where n is number and A,B,C,D are molecules, where as for first order reactions Keq is calculated. Kd for higher order reactions is not considered.
  Name KfKbKdtauSubstrateProduct
1 basal-activitykf
(s^-1)
0
(s^-1)
--CaMKII
CaMKII-thr286
  This reaction represents one of the big unknowns in CaMK-II biochemistry: what maintains the basal level of phosphorylation on thr 286 ? See Hanson and Schulman Ann Rev Biochem 1992 61:559-601, specially pg 580, for review. I have not been able to find any compelling mechanism in the literature, but fortunately the level of basal activity is well documented.
2 CaMK-thr286-bind
-CaM
kf
(uM^-1 s^-1)
0.1
(s^-1)
Kd(bf) = 0.0001(uM)-CaMKII-thr286
CaM-Ca4
  • CaMKII-thr286*-C
    aM

  •   Affinity is up 1000X. Time to release is about 20 sec, so the kb is OK at 0.1 This makes Kf around 1.6666e-3
    3 CaMKII-bind-CaMkf
    (uM^-1 s^-1)
    5
    (s^-1)
    Kd(bf) = 0.1(uM)-CaM-Ca4
    CaMKII
    CaMKII-CaM
      This is tricky. There is some cooperativity here arising from interactions between the subunits of the CAMKII holoenzyme. However, the stoichiometry is 1. Kb/Kf = 6e4 #/cell. Rate is fast (see Hanson et al Neuron 12 943-956 1994) so lets say kb = 10. This gives kf = 1.6667e-4 H&S AnnRev Biochem 92 give tau for dissoc as 0.2 sec at low Ca, 0.4 at high. Low Ca = 100 nM = physiol.


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