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Molecule Parameter List for temp-PIP2

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
temp-PIP2 participated asMoleculeSum total ofEnzymeSubstrate of an enzymeProduct of an enzymeSubstrate in ReactionProduct in Reaction
No. of occurrences1000020

Accession and Pathway Details
Accession NameAccession No.Accession TypePathway Link
  • Synaptic_
    Network
  • 16Network
    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

    temp-PIP2 acting as a Molecule in  
    Synaptic_Network Network
    NameAccession NamePathway NameInitial Conc.
    (uM)
    Volume
    (fL)
    Buffered
    temp-PIP2
  • Synaptic_
    Network

    Accession No. : 16
  • Shared_Object_
    Synaptic_
    Network

    Pathway No. : 70
  • 2.51000Yes
    This is a steady PIP2 input to PLA2. The sensitivity of PLA2 to PIP2 discussed below does not match with the reported free levels which are used by the phosphlipase Cs. My understanding is that there may be different pools of PIP2 available for stimulating PLA2 as opposed to being substrates for PLCs. For that reason I have given this PIP2 pool a separate identity. As it is a steady input this is not a problem in this model. Majerus et al Cell 37:701-703 report a brain concentration of 0.1 - 0.2 mole % Majerus et al Science 234:1519-1526 report a huge range of concentrations: from 1 to 10% of PI content, which is in turn 2-8% of cell lipid. This gives 2e-4 to 8e-3 of cell lipid. In concentrations in total volume of cell (a somewhat strange number given the compartmental considerations) this comes to anywhere from 4 uM to 200 uM. PLA2 is stim 7x by PIP2 (Leslie and Channon BBA 1045:261(1990) Leslie and Channon say PIP2 is present at 0.1 - 0.2mol% range in membs, so I'll use a value at the lower end of the scale for basal PIP2.

    temp-PIP2 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.
     NameAccession NamePathway NameKfKbKdtauReagents
    1PIP2-PLA2-act
  • Synaptic_
    Network

    Accession No. : 16
  • PLA2
    Pathway No. : 72
    0.0012
    (uM^-1 s^-1)
    0.5
    (s^-1)
    Kd(bf) = 416.6667(uM)-Substrate
    PLA2-cytosolic
    temp-PIP2

    Product
    PIP2-PLA2*
      Activation of PLA2 by PIP2. From Leslie and Channon 1990 BBA 1045:261 the stimulation of PLA2 activity by high PIP2 is 7x. In this model we don't really expect any PIP2 stimulus.
    2
  • PIP2-Ca-PLA2-act
  • Synaptic_
    Network

    Accession No. : 16
  • PLA2
    Pathway No. : 72
    0.012
    (uM^-1 s^-1)
    0.1
    (s^-1)
    Kd(bf) = 8.3333(uM)-Substrate
    PLA2-Ca*
    temp-PIP2

    Product
    PIP2-Ca-PLA2*
      Synergistic activation of PLA2 by Ca and PIP2. Again from Leslie and Channon 1990 BBA 1045:261



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