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Accession Type:
Network
Osc_Ca_
IP3metabolism
MIPP
CaMKII
CaM
PKC
IP3-3K
Gq
PLCbeta
 Molecule
 Enzyme
 Reaction
134_dephos
145_dephos
IP4-system
IHP-system
1345_dephos
CaRegulation
Othmer-Tang-mode
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Reaction List for pathway PLCbeta (Pathway Number 126)

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 Act-PLC-by-Gqkf
(uM^-1 s^-1)
1
(s^-1)
Kd(bf) = 0.0397(uM)-PLC-Ca
G*GTP
PLC-Ca-Gq
  Affinity for Gq is > 20 nM (Smrcka et al Science251 804-807 1991) so [Gq].kf = kb so 40nM * 6e5 = kb/kf = 24e3 so kf = 4.2e-5, kb =1
2 Act-PLC-Cakf
(uM^-1 s^-1)
1
(s^-1)
Kd(bf) = 0.3333(uM)-Ca
PLC
PLC-Ca
  Affinity for Ca = 1uM without AlF, 0.1 with: from Smrcka et al science 251 pp 804-807 1991 so [Ca].kf = kb so kb/kf = 1 * 6e5 = 1/1.66e-6 Assigned affinity to a Kd of 0.333 to maintain balance.
3 basalkf
(s^-1)
0
(uM^-1 s^-1)
--PIP2
DAG
IP3(145)
  accounts for other PLC isoforms that contribute to basal levels of IP3
4 Degrade-DAGkf
(s^-1)
0
(s^-1)
--DAG
PC
  Rate based on basal and activated levels of DAG
5 Inact-PLC-Gqkf
(s^-1)
0
(uM^-1 s^-1)
--PLC-Ca-Gq
PLC-Ca
G*GDP
  Rate of 100/min to account for GAP activity of PLC: Biddlecome et al, JBC, 271, 14, 7999-8007, 1996
6 PLC-bind-Gqkf
(uM^-1 s^-1)
1
(s^-1)
Kd(bf) = 0.3968(uM)-PLC
G*GTP
PLC-Gq
  this binding does not produce active PLC. This step was needed to implement the described (Smrcka et al) increase in affinity for Ca by PLC once Gq was bound. The tempkin are the same as the binding step for Ca-PLC to Gq. Kd is constrained by detailed balance.
7 PLC-Gq-bind-Cakf
(uM^-1 s^-1)
1
(s^-1)
Kd(bf) = 0.0333(uM)-PLC-Gq
Ca
PLC-Ca-Gq
  this step has a high affinity for Ca, from Smrcka et al. 0.1uM so kf /kb = 1/6e4 = 1.666e-5:1. See the Act-PLC-by-Gq reaction. Raised kf to 5e-5 based on match to conc-eff curves from Smrcka et al.


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