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Molecule Parameter List for G*GTP

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
G*GTP participated asMoleculeSum total ofEnzymeSubstrate of an enzymeProduct of an enzymeSubstrate in ReactionProduct in Reaction
No. of occurrences1000032

Accession and Pathway Details
Accession NameAccession No.Accession TypePathway Link
  • Osc_Ca_
    IP3metabolism
  • 32Network
    MIPP CaMKII CaM 
    PKC IP3-3K Gq 
    PLCbeta 134_dephos 145_dephos 
    IP4-system IHP-system 1345_dephos 
    CaRegulation Othmer-Tang-model 
    This network models an oscillatory calcium response to GPCR mediated PLCbeta activation, alongwith detailed InsP3 metabolism in the neuron. It is similar to the Osc_Ca_IP3metab model (accession 24) except that some enzymes in the InsP3 metabolism network have been modified to have reversible kinetics rather than Michaelis-Menten kinetics. The modified enzymes belong to the groups: IP4-system, IP3-3K, 145_dephos and 134_dephos. Mishra J, Bhalla US. Biophys J. 2002 Sep;83(3):1298-316.

    G*GTP acting as a Molecule in  
    Osc_Ca_IP3metabolism Network
    NameAccession NamePathway NameInitial Conc.
    (uM)
    Volume
    (fL)
    Buffered
    G*GTP
  • Osc_Ca_
    IP3metabolism

    Accession No. : 32
  • Gq
    Pathway No. : 163
    01000No
    Activated G protein. Berstein et al indicate that about 20-40% of the total Gq alpha should bind GTP at steady stimulus.

    G*GTP acting as a Substrate in a reaction in  
    Osc_Ca_IP3metabolism 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.
     NameAccession NamePathway NameKfKbKdtauReagents
    1Inact-G
  • Osc_Ca_
    IP3metabolism

    Accession No. : 32
  • Gq
    Pathway No. : 163
    0.0133
    (s^-1)
    0
    (s^-1)
    --Substrate
    G*GTP

    Product
    G*GDP
      From Berstein et al JBC 267:12 8081-8088 1992, kcat for GTPase activity of Gq is only 0.8/min.
    2PLC-bind-Gq
  • Osc_Ca_
    IP3metabolism

    Accession No. : 32
  • PLCbeta
    Pathway No. : 164
    2.52
    (uM^-1 s^-1)
    1
    (s^-1)
    Kd(bf) = 0.3968(uM)-Substrate
    G*GTP
    PLC

    Product
    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.
    3Act-PLC-by-Gq
  • Osc_Ca_
    IP3metabolism

    Accession No. : 32
  • PLCbeta
    Pathway No. : 164
    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

    G*GTP acting as a Product in a reaction in  
    Osc_Ca_IP3metabolism 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.
     NameAccession NamePathway NameKfKbKdtauReagents
    1Basal-Act-G
  • Osc_Ca_
    IP3metabolism

    Accession No. : 32
  • Gq
    Pathway No. : 163
    0.0001
    (s^-1)
    0
    (uM^-1 s^-1)
    --Substrate
    G-GDP

    Product
    BetaGamma
    G*GTP
      This is the basal exchange of GTP for GDP. So slow as to be nearly negligible.
    2Activate-Gq
  • Osc_Ca_
    IP3metabolism

    Accession No. : 32
  • Gq
    Pathway No. : 163
    0.01
    (s^-1)
    0
    (uM^-2 s^-1)
    --Substrate
    Rec-Glu-Gq

    Product
    BetaGamma
    G*GTP
    Rec-Glu
      This reaction is the critical one for activation of Gq. It probably encapsulates multiple steps. In this approximation the receptor-ligand- Gprotein complex splits up into GTP.Galpha, rec.ligand complex, and Gbetagamma. There is a hidden step of exchange of GDP for GTP. The reaction does not take these into account since it is assumed that both GTP and GDP levels are tightly regulated by metabolic control. This is the kcat==k3 stage of the Rec-Glu ezymatic activation of Gq. From Berstein et al actiation is at .35 - 0.7/min From Fay et al Biochem 30 5066-5075 1991 kf = .01/sec From Nakamura et al J physiol Lond 474:1 35-41 1994 see time courses. Also (Berstein) 15-40% of gprot is in GTP-bound form on stim.



    Database compilation and code copyright (C) 2022, Upinder S. Bhalla and NCBS/TIFR
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