| |
Reaction
Name | Pathway Name /
Pathway No. | Kf | Kb | Kd | tau | Reagents |
| 1 | Ca-bind-CaNAB | PP2B
Pathway No. 83 | 10008
(uM^-2 s^-1) | 1
(s^-1) | Kd(af) = 0.01(uM) | - | Substrate:
CaNAB
Ca
Ca
Products:
CaNAB-Ca2
|
| going on the experience with CaM, we put the fast (high affinity) sites first. We only know (Stemmer and Klee) that the affinity is < 70 nM. Assuming 10 nM at first. This doesn't really matter much because it will always be bound at physiological Ca. | | 2 | Ca-bind-to-Trans
p | CaRegulation
Pathway No. 86 | 3600
(uM^-2 s^-1) | 144
(s^-1) | Kd(bf) = 0.04(uM) | - | Substrate:
Ca_intracell
Ca_intracell
CaTransp
Products:
CaTransp-2Ca
|
| Rates from Lauffenberger and Linderman 1993 Receptors pg 200. Kd = KCa2 = 0.2 uM. | | 3 | CaMK-thr286-bind
-CaM | CaMKII
Pathway No. 80 | 1000.2
(uM^-1 s^-1) | 0.1
(s^-1) | Kd(bf) = 0.0001(uM) | - | Substrate:
CaMKII-thr286
CaM-Ca4
Products:
CaMKII-thr286*-C
aM
|
| Affinity is up 1000X over the unphosphorylated CaMKII, which makes the Kd of 0.1 nM. See Hanson et al 1994 Neuron 12:943-956. Time to release is about 20 sec, so the kb is OK at 0.1/sec. as tested by a few runs. | | 4 | Gs-bind-AC2* | AC
Pathway No. 85 | 833.28
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0012(uM) | - | Substrate:
Gs-alpha
AC2*
Products:
AC2*-Gs
|
| Various references: Jacobowitz et al JBC 268(6):3829-3892 show that AC2 has a 2x rise in basal activation on phosphorylation, and a 2x rise in forskolin stimulated activation. Yoshimura and Cooper JBC 1993 268(7):4604-4607 say that type II is stimulated 9x over basal. Lustig et al 1993 JBC 268(19):13900-13905 syow a 2x activation by PDBu, and the Gs stimulated response is increased 2x-4x by PDBu. To match all these results with the binding of the unphosphorylated form we use a Kd of 1.2 nM here as compared with the Kd of 2 nM for the unphosphorylated reaction. | | 5 | CaM_bind_PDE1 | AC
Pathway No. 85 | 720
(uM^-1 s^-1) | 5
(s^-1) | Kd(bf) = 0.0069(uM) | - | Substrate:
PDE1
CaM-Ca4
Products:
CaM.PDE1
|
| Borisy et al J Neurosci 12(3):915-923 For olf epithelium PDE1, affinity is 7 nM CaM and about 2 uM Ca which is consistent with it binding Ca4.CaM at 7 nM. Assume same for brain. Reaction should be pretty fast. Assume kb = 5/sec. | | 6 | CaMCa4-bind-CaNA
B | PP2B
Pathway No. 83 | 600
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0017(uM) | - | Substrate:
CaM-Ca4
CaNAB-Ca4
Products:
CaMCa4-CaNAB
|
| This step is the starting point for calculating all the CaM-binding steps to CaNAB-Ca4. The calculation goes like this: From Stemmer and Klee 1994 Biochem 33 6859-6866 we have rates for Ca binding to CaM.Ca4.CaN. From detailed balance (Kd must be 1 around a loop) we can set ratios of Kds for CaMCa3 binding to CaN, and CaM-Ca2 binding to CaN. Thus those rates can come once we know the Kd for the current reaction of CaMCa4 binding to CaN. We'll ignore the Ca binding steps to CaM.Ca4.CaN since the reactions around the remaining part of the loop will settle pretty fast to the same levels. Finally, we estimate the kf=0.001 here from a series of simulations matching the curves in Stemmer and Klee. | | 7 | remove_glu | Shared_Object_
Synaptic_
Network
Pathway No. 70 | 500
(s^-1) | 1000
(s^-1) | Keq = 2(uM) | 0.001sec | Substrate:
Glu
Products:
synapse
|
| This reaction doubles for arrival as well as removal of glu from the synapse. Assume tau for removal of glu is ~1 msec. We know that diffusion time for arrival of glu from presynaptic side is < 50 usec. Most of the actual synaptic delay has to do with binding to the receptors. | | 8 | Gs-bind-AC2 | AC
Pathway No. 85 | 499.998
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.002(uM) | - | Substrate:
AC2
Gs-alpha
Products:
AC2-Gs
|
| Half-max at around 3nM = kb/kf from fig 5 in Feinstein et al PNAS USA 88 10173-10177 1991 kf = kb/1800 = 5.56e-4 kb Ofer Jacobowitz's thesis data indicates it is more like 2 nM. Jacobowitz, PhD Thesis, Mount Sinai School of Medicine. | | 9 | Inact-PP1 | PP1
Pathway No. 82 | 499.98
(uM^-1 s^-1) | 0.1
(s^-1) | Kd(bf) = 0.0002(uM) | - | Substrate:
I1*
PP1-active
Products:
PP1-I1*
|
| K inhib = 1nM from Cohen Ann Rev Bioch 1989, 4 nM from Foukes et al Assume 2 nM. kf /kb = 8.333e-4 The Kd used here is 0.2 nM. This is small, but unlikely to matter much as the affinity is so strong that the reaction will be all the way forward in either case. Tau < 1 min for inhibition. Stralfors 1985 Eur J Biochem 149:295-303 fig 8 pg 201. | | 10 | Ca_act_PLC_g | PLC_g
Pathway No. 79 | 180
(uM^-1 s^-1) | 10
(s^-1) | Kd(bf) = 0.0556(uM) | - | Substrate:
PLC_g
Ca
Products:
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. | | 11 | Gs-bind-AC1 | AC
Pathway No. 85 | 126
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0079(uM) | - | Substrate:
Gs-alpha
AC1
Products:
AC1-Gs
|
| Half-max 8nM from Tang et al JBC266:13 8595-8603 kb/kf = 8 nM = 4800#/cell Also assume rapid binding of 1/sec. | | 12 | cAMP-bind-site-A
1 | PKA
Pathway No. 84 | 75
(uM^-1 s^-1) | 110
(s^-1) | Kd(bf) = 1.4667(uM) | - | Substrate:
R2C2-cAMP2
cAMP
Products:
R2C2-cAMP3
|
| This site has a higher Kd for cAMP. See Ogreid and Doskeland 1982 FEBS Lett 150:1 161-166 | | 13 | cAMP-bind-site-A
2 | PKA
Pathway No. 84 | 75
(uM^-1 s^-1) | 32.5
(s^-1) | Kd(bf) = 0.4333(uM) | - | Substrate:
cAMP
R2C2-cAMP3
Products:
R2C2-cAMP4
|
| Cooperativity kicks in, now we have a low Kd for cAMP. | | 14 | CaM-TR2-bind-Ca | CaM
Pathway No. 81 | 72
(uM^-2 s^-1) | 72
(s^-1) | Kd(af) = 1(uM) | - | Substrate:
CaM
Ca
Ca
Products:
CaM-TR2-Ca2
|
| We use the Martin et al 1985 Eur J Biochem 151(3):543-550 rates here, plus the Drabikowski and Brzeska 1982 JBC 257(19):11584-11590 binding consts. All are scaled by 3X to cell temperature. kf = 2e-10 kb = 72 Stemmer & Klee 1994 Biochem 33:6859-6866 have values of : K1=.9, K2=1.1. Assume 1.0uM for both | | 15 | Antag-bind-Rec-G
q | Gq
Pathway No. 74 | 60
(uM^-1 s^-1) | 0.01
(s^-1) | Kd(bf) = 0.0002(uM) | - | Substrate:
Rec-Gq
mGluRAntag
Products:
Blocked-rec-Gq
|
| The rate consts give a total binding affinity of under 0.2 nM, good for a strong antagonist. | | 16 | CaM-bind-GEF | Ras
Pathway No. 76 | 60
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0167(uM) | - | Substrate:
inact-GEF
CaM-Ca4
Products:
CaM-GEF
|
| We have no numbers for this. It is probably between the two extremes represented by the CaMKII phosph states, and I have used guesses based on this. kf=1e-4 kb=1 The reaction is based on Farnsworth et al Nature 376 524-527 1995 | | 17 | Release-C1 | PKA
Pathway No. 84 | 60
(s^-1) | 18
(uM^-1 s^-1) | Kd(cb) = 0.3(uM) | - | Substrate:
R2C2-cAMP4
Products:
PKA-active
R2C-cAMP4
|
| The complex starts to dissociate and release the catalytic subunit C. This has to be fast, as the activation of PKA by cAMP is also fast. | | 18 | Release-C2 | PKA
Pathway No. 84 | 60
(s^-1) | 18
(uM^-1 s^-1) | Kd(cb) = 0.3(uM) | - | Substrate:
R2C-cAMP4
Products:
PKA-active
R2-cAMP4
|
| Second catalytic subunit is now released. | | 19 | inhib-PKA | PKA
Pathway No. 84 | 60
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0167(uM) | - | Substrate:
PKA-active
PKA-inhibitor
Products:
inhibited-PKA
|
| See Doskeland and Ogreid Int J Biochem 13:1-19. Not clear what the rates are, but the reaction has to be fast and it has to have a pretty high affinity. The exact values are not critical under these conditions. | | 20 | cAMP-bind-site-B
1 | PKA
Pathway No. 84 | 54
(uM^-1 s^-1) | 33
(s^-1) | Kd(bf) = 0.6111(uM) | - | Substrate:
R2C2
cAMP
Products:
R2C2-cAMP
|
| Hasler et al FASEB J 6:2734-2741 1992 say Kd =1e-7M for type II, 5.6e-8 M for type I. Smith et al PNAS USA 78:3 1591-1595 1981 say that Ka1 is 2.1e7/M which gives a Kd of 47 nM, Kan = 5e8/M or Kd of 2nM. I prefer numbers from Ogreid and Doskeland Febs Lett 129:2 287-292 1981. Their conditions are more physiological. They have figs suggesting time course of complete assoc is < 1 min. |
and 
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