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Molecule Parameter List for Ca.PLC_g* | The statistics table lists the distribution of a molecule acting either as a substrate, product, enzyme or as a molecule within the network.
The text color of a molecule is highlighted by  color. | | Statistics |
Accession and Pathway Details | |
| Accession Name | Accession No. | Accession Type | Pathway Link | Synaptic_
Network | 16 | Network |
Shared_Object_Synaptic_Network, PKC, PLA2,
PLCbeta, Gq, MAPK,
Ras, EGFR, Sos,
PLC_g, CaMKII, CaM,
PP1, PP2B, PKA,
AC, CaRegulation | This model is an annotated version of the synaptic signaling network.
The primary reference is Bhalla US and Iyengar R. Science (1999) 283(5400):381-7 but several of the model pathways have been updated.
Bhalla US Biophys J. 2002 Aug;83(2):740-52
Bhalla US J Comput Neurosci. 2002 Jul-Aug;13(1):49-62 |
Ca.PLC_g* acting as a Molecule in Synaptic_Network Network
| Name | Accession Name | Pathway Name | Initial Conc.
(uM) | Volume
(fL) | Buffered | | Ca.PLC_g* | Synaptic_
Network
Accession No. : 16 | PLC_g
Pathway No. : 79 | 0 | 1000 | No | | |
Ca.PLC_g* acting as an Enzyme in Synaptic_Network Network
Enzyme Molecule /
Enzyme Activity | Accession Name | Pathway Name | Km (uM) | kcat (s^-1) | Ratio | Enzyme Type | Reagents | Ca.PLC_g* /
PIP2_hydrolysis
| Synaptic_
Network
Accession No. : 16 | PLC_g
Pathway No. : 79 | 19.7917 | 57 | 4 | Classical Michaelis-Menten
V = Etot.S.Kcat/Km+S | Substrate
PIP2
Product
DAG
IP3
| | Mainly Homma et al JBC 263:14 1988 pp 6592. These parms are the Ca-stimulated form. Wahl et al JBC 267:15 10447-10456 1992 say that the tyrosine phosphorylated form has 7X higher affinity for substrate than control. The PIP2 levels in this model are rather low, at 10 uM. |
Ca.PLC_g* acting as a Product of an Enzyme in Synaptic_Network Network
Enzyme Molecule /
Enzyme Activity | Accession Name | Pathway Name | Km (uM) | kcat (s^-1) | Ratio | Enzyme Type | Reagents | L.EGFR /
phosph_PLC_g | Synaptic_
Network
Accession No. : 16 | EGFR
Pathway No. : 77 | 0.333333 | 0.2 | 4 | explicit E-S complex | Substrate
Ca.PLC_g
Product
Ca.PLC_g*
| | Hsu et al JBC 266:1 603-608 1991 Km = 385 +- 100 uM, Vm = 5.1 +-1 pmol/min/ug for PLC-771. Other sites have similar range, but are not stim as much by EGF. These rates are improbably slow and are for the intracellular domain of EGFR alone. Wahl et al JBC 267(15) 10447-10456 1992 reports a tau of 5min for activation of PLC-gamma in vivo. Also Sherrill and Kyte say turnover # for angiotensin II is 5/min for cell extt, and 2/min for placental. Also see Okada et al JBC 270(35) 20737-20741 1995 for Shc rates where Km = 0.7 and Vmax = 4.4 pmol/min To achieve these turnovers and time-courses, we may need to consider the membrane-plane action of the the receptor, but for now the rates are consistent with the Wahl et al reports. |
Ca.PLC_g* acting as a Substrate in a reaction in Synaptic_Network Network
| 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 reaction are not consider. |
| Name | Accession Name | Pathway Name | Kf | Kb | Kd | tau | Reagents | | dephosph_PLC_g | Synaptic_
Network
Accession No. : 16 | PLC_g
Pathway No. : 79 | 0.05
(s^-1) | 0
(s^-1) | - | - | Substrate
Ca.PLC_g*
Product
Ca.PLC_g
| | This is a generic balancing dephosphorylation step for the PLC. Rates are determined by considering balance between phosph and non-phosph forms of PLC-gamma. Wahl et al JBC 267(15) 10447-10456 1992 put the ratio at 50% phosph form in cytoplasm, about 20% in membrane. |
Ca.PLC_g* acting as a Product in a reaction in Synaptic_Network Network
| 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 reaction are not consider. |
| Name | Accession Name | Pathway Name | Kf | Kb | Kd | tau | Reagents | | Ca_act_PLC_g* | Synaptic_
Network
Accession No. : 16 | PLC_g
Pathway No. : 79 | 12
(uM^-1 s^-1) | 10
(s^-1) | Kd(bf) = 0.8333(uM) | - | Substrate
Ca
PLC_G*
Product
Ca.PLC_g*
| | Again, we refer to Homma et al and Wahl et al, for preference using Wahl et al JBC 267(15):10447-10456 1992. Half-Max of the phosph form is at 316 nM. Use kb of 10 as this is likely to be pretty fast. As we are phosphorylating the Ca-bound form, equils have shifted. kf should now be 2e-5 (Kf = 12) to match the reported half-max. |
| Database compilation and code copyright (C) 2022, Upinder S. Bhalla and NCBS/TIFR
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