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Accession Type:
Network
NonOsc_Ca_
IP3metabolism
MIPP
CaMKII
CaM
PKC
IP3-3K
CaRegulation
 Molecule
 Enzyme
 Reaction
Gq
PLCbeta
134_dephos
145_dephos
IP4-system
IHP-system
1345_dephos

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Reaction List for pathway CaRegulation (Pathway Number 110)

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 reactions is not considered.
  Name KfKbKdtauSubstrateProduct
1 Ca-bind-to-Trans
p
kf
(uM^-2 s^-1)
144
(s^-1)
Kd(af) = 0.2(uM)-Ca
Ca
CaTransp
CaTransp-2Ca
  Rates from Lauffenburger abd Linderman 1993 Receptors pg 200. Kd = KCa2 = 0.2 uM
2 Ca10-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Ca5-Cal
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca10-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with Ca5-Cal. Due to system limitations only four are entered.
3 Ca15-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Ca10-Cal
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca15-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with Ca10-Cal. Due to system limitations only four are entered.
4 Ca20-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Ca15-Cal
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca20-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with Ca15-Cal. Due to system limitations only four are entered.
5 Ca25-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca20-Cal
Ca25-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with Ca20-Cal. Due to system limitations only four are entered.
6 Ca30-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Ca25-Cal
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca30-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with Ca25-Cal. Due to system limitations only four are entered.
7 Ca35-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca30-Cal
Ca35-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with Ca30-Cal. Due to system limitations only four are entered.
8 Ca40-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca35-Cal
Ca40-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with Ca35-Cal. Due to system limitations only four are entered.
9 Ca5-bind-Calkf
(uM^-5 s^-1)
1
(s^-1)
--Calseq
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca-sequester
Ca5-Cal
  There are actually 5 Ca-sequester substrates for this reaction, along with one Calseq. Due to system limitations only four are entered.
10 CaTraspATPasekf
(s^-1)
0
(#^-2 s^-1)
Not applicable**-CaTransp-2Ca
CaTransp
Ca-sequester
Ca-sequester
  kCa3 = 2 * Ca transporter rate since each step has 2 Ca++. = 0.5 uM/sec from Lauffenburger and Linderman 1993 Receptors pg200 The amount of the activated transporter is about 0.01 uM = 6e3#. from runs. So 0.01uM * kf * 2 = 0.5 uM/sec (no back reaction) so kf = 25, kb = 0 Alternatively, 6e3 * kf = 0.25 * 6e5, giving the same kf
11 inactivate_cap_
Ca
kf
(#^-2 s^-1)
1
(s^-1)
Not applicable**-Ca-sequester
Ca-sequester
  • capacitive_Ca_
    entry*

  • inact_cap_entry
      The Kd is set at about 3 uM so that at resting Ca the capacitative Ca entry is almost blocked. A 2nd order response makes the response steep.
    12 IP3Rbindkf
    (uM^-3 s^-1)
    1
    (s^-1)
    Kd(af) = 2.7144(uM)-IP3R
    IP3
    IP3
    IP3
    IP3R*
      Based on Lauffenburger and Linderman 1993 Receptors pg 200. The binding of IP3 on this reaction had a Hill coeff of 3. The eqns of Mahama and Linderman (cited in the book as 1993 a) are equivalent to the binding all occurring in a single step, so that is how I do it in this version. Their Ki1 is 0.07 uM. Lots of other data sources: Ramos-Franco et al, Biophys J 75, 1998: 834-39 have Ca sensitivity curves. At 250 nM free Ca, the EC50 for type1 is 58 nM and type 2 is 194 nM. Type 3 would be about 2 uM according to Newton et al, JBC 268(46), 1994: 28613-19. For the purposes of this model we use a Kd of 2.7 uM which is high but maybe OK at low calcium. The details of Ca interaction with the IP3R are not included in this model.


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