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Molecule Parameter List for IP3

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
IP3 participated asMoleculeSum total ofEnzymeSubstrate of an enzymeProduct of an enzymeSubstrate in ReactionProduct in Reaction
No. of occurrences1000410

Accession and Pathway Details
Accession NameAccession No.Accession TypePathway Link
  • MAPK_network_
    2003
  • 50Network
    Shared_Object_MAPK_network_2003 PKC PLA2 
    PLCbeta Gq MAPK 
    Ras EGFR Sos 
    PLC_g CaMKII CaM 
    PP1 PP2B PKA 
    AC 
    This is a network model of many pathways present at the neuronal synapse. The network has properties of temporal tuning as well as steady-state computational properties. In its default form the network is bistable.Bhalla US Biophys J. 2004 Aug;87(2):745-53

    IP3 acting as a Molecule in  
    MAPK_network_2003 Network
    NameAccession NamePathway NameInitial Conc.
    (uM)
    Volume
    (fL)
    Buffered
    IP3
  • MAPK_network_
    2003

    Accession No. : 50
  • Shared_Object_
    MAPK_network_
    2003

    Pathway No. : 206
  • 0.731000No
    Peak IP3 is perhaps 15 uM, basal <= 0.2 uM.

    IP3 acting as a Product of an Enzyme in  
    MAPK_network_2003 Network
     Enzyme Molecule /
    Enzyme Activity
    Accession NamePathway NameKm (uM)kcat (s^-1)RatioEnzyme TypeReagents
    1PLC-Ca  /
    PLC-Ca
  • MAPK_network_
    2003

    Accession No. : 50
  • PLCbeta
    Pathway No. : 209
    19.8413104explicit E-S complexSubstrate
    PIP2

    Product
    DAG
    IP3
        From Sternweis et al Phil Trans R Soc Lond 1992, also matched by Homma et al. k1 = 1.5e-5, now 4.2e-6 k2 = 70/sec; now 40/sec k3 = 17.5/sec; now 10/sec Note that the wording in Sternweis et al is ambiguous re the Km.
    2PLC-Ca-Gq  /
    PLCb-Ca-Gq
  • MAPK_network_
    2003

    Accession No. : 50
  • PLCbeta
    Pathway No. : 209
    5484explicit E-S complexSubstrate
    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. k1 = 5e-5/sec k2 = 240/sec; now 120/sec k3 = 60/sec; now 30/sec Note that the wording in Sternweis et al is ambiguous wr. to the Km for Gq vs non-Gq states of PLC. K1 is still a bit too low. Raise to 7e-5 9 Jun 1996: k1 was 0.0002, changed to 5e-5
    3Ca.PLC_g  /
    PIP2_hydrolysis
  • MAPK_network_
    2003

    Accession No. : 50
  • PLC_g
    Pathway No. : 215
    97.2222144Classical Michaelis-Menten
    V = Etot.S.Kcat/Km+S
    Substrate
    PIP2

    Product
    DAG
    IP3
        Mainly Homma et al JBC 263:14 1988 pp 6592, but these parms are the Ca-stimulated form. It is not clear whether the enzyme is activated by tyrosine phosphorylation at this point or not. Wahl et al JBC 267:15 10447-10456 1992 say that the Ca_stim and phosph form has 7X higher affinity for substrate than control. This is close to Wahl's figure 7, which I am using as reference.
    4Ca.PLC_g*  /
    PIP2_hydrolysis
  • MAPK_network_
    2003

    Accession No. : 50
  • PLC_g
    Pathway No. : 215
    19.7917574Classical Michaelis-Menten
    V = Etot.S.Kcat/Km+S
    Substrate
    PIP2

    Product
    DAG
    IP3
        Mainly Homma et al JBC 263:14 1988 pp 6592, but these parms are the Ca-stimulated form. It is not clear whether the enzyme is activated by tyrosine phosphorylation at this point or not. Wahl et al JBC 267:15 10447-10456 1992 say that this has 7X higher affinity for substrate than control.

    IP3 acting as a Substrate in a reaction in  
    MAPK_network_2003 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
    Degrade-IP3
  • MAPK_network_
    2003

    Accession No. : 50
  • PLCbeta
    Pathway No. : 209
    2.5
    (s^-1)
    0
    (s^-1)
    --Substrate
    IP3

    Product
    Inositol
    The enzyme is IP3 5-phosphomonesterase. about 45K. Actual products are Ins(1,4)P2, and cIns(1:2,4,5)P3. review in Majerus et al Science 234 1519-1526, 1986. Meyer and Stryer 1988 PNAS 85:5051-5055 est decay of IP3 at 1-3/sec



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