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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 | 97.2222 | 14 | 4 | Classical Michaelis-Menten
V = Etot.S.Kcat/Km+S | Substrate
PIP2
Product
DAG
IP3
| | Wahl et al JBC 267(15) 10447-10456 1992. Homma et al JBC 263:14 1988 pp 6592. These parms are the Ca-stimulated form. This is close to Wahl's figure 7, which I am using as reference. Also see Nakanishi et al Biochem J 256 453-459 1998, Nishibe et al Science 250 :1253-1256 This model uses a rather low PIP2 of 10 uM. |
Ca.PLC_g acting as a Substrate for 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 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 | Ca_act_PLC_g | Synaptic_
Network
Accession No. : 16 | PLC_g
Pathway No. : 79 | 180
(uM^-1 s^-1) | 10
(s^-1) | Kd(bf) = 0.0556(uM) | - | Substrate
Ca
PLC_g
Product
Ca.PLC_g
| | | Nice curves from Homma et al JBC 263:14 6592-6598 1988 Fig 5c. The activity falls above 10 uM, but that is too high to reach physiologically anyway, so we'll ignore the higher pts and match the lower ones only. Half-max at 1 uM. But Wahl et al JBC 267:15 10447-10456 1992 have half-max at 56 nM which is what I'll use. | | 2 | 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. |
| Database compilation and code copyright (C) 2022, Upinder S. Bhalla and NCBS/TIFR
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