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Molecule Parameter List for PLC-Ca-Gq | 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 |
PLC-Ca-Gq acting as a Molecule in Synaptic_Network Network
| Name | Accession Name | Pathway Name | Initial Conc.
(uM) | Volume
(fL) | Buffered | | PLC-Ca-Gq | Synaptic_
Network
Accession No. : 16 | PLCbeta
Pathway No. : 73 | 0 | 1000 | No | | This should really be labelled Ca.GTP.Gq_alpha.PLC This is the activated form of the enzyme. |
PLC-Ca-Gq 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 | PLC-Ca-Gq /
PLCb-Ca-Gq
| Synaptic_
Network
Accession No. : 16 | PLCbeta
Pathway No. : 73 | 5 | 48 | 4 | explicit E-S complex | Substrate
PIP2
Product
DAG
IP3
| | From Sternweis et al, Phil Trans R Soc Lond 1992, and the values from other refs eg Homma et al JBC 263(14) pp6592 1988 match. In this model I have rather low values for PIP2. The Km values are low to match. Sternweis mentions a 5 uM Km which is what I use here, but the Homma paper suggests about 20x higher Km, which would also fit with 20x higher PIP2. So that parameter, though it is off, cancels out and the overall rate would be the same. Vmax is about 23 umol/min/mg at high Ca from Sternweis or about 60/sec. This model value is a little lower than that. |
PLC-Ca-Gq 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 | | Inact-PLC-Gq | Synaptic_
Network
Accession No. : 16 | PLCbeta
Pathway No. : 73 | 0.0133
(s^-1) | 0
(uM^-1 s^-1) | - | - | Substrate
PLC-Ca-Gq
Product
G*GDP
PLC-Ca
| | This process is assumed to be directly caused by the inactivation of the G*GTP to G*GDP. Hence, kf = .013 /sec = 0.8/min, same as the rate for Inact-G. kb = 0 since this is irreversible. We may be interested in studying the role of PLC as a GAP. If so, the kf would be faster here than in Inact-G |
PLC-Ca-Gq 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 | | 1 | Act-PLC-by-Gq | Synaptic_
Network
Accession No. : 16 | PLCbeta
Pathway No. : 73 | 25.2
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0397(uM) | - | Substrate
G*GTP
PLC-Ca
Product
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 | PLC-Gq-bind-Ca | Synaptic_
Network
Accession No. : 16 | PLCbeta
Pathway No. : 73 | 30
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0333(uM) | - | Substrate
Ca
PLC-Gq
Product
PLC-Ca-Gq
| | | this step has a high affinity of 0.1 uM for Ca, from Smrcka et al 1991 Science 251:804-807 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. |
| Database compilation and code copyright (C) 2022, Upinder S. Bhalla and NCBS/TIFR
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