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Molecule Parameter List for AC2* | 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 |
Accession and Pathway Details | |
| Accession Name | Accession No. | Accession Type | Pathway Link | Synaptic_
Network | 16 | Network |
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 |
AC2* acting as a Molecule in Synaptic_Network Network
| Name | Accession Name | Pathway Name | Initial Conc.
(uM) | Volume
(fL) | Buffered | | AC2* | Synaptic_
Network
Accession No. : 16 | AC
Pathway No. : 85 | 0 | 1000 | No | | This is the phosphorylation-activated form of AC2. |
AC2* acting as an Enzyme in Synaptic_Network Network
Enzyme Molecule /
Enzyme Activity | Accession Name | Pathway Name | Km (uM) | kcat (s^-1) | Ratio | Enzyme Type | Reagents | AC2* /
kenz
| Synaptic_
Network
Accession No. : 16 | AC
Pathway No. : 85 | 20.1149 | 7 | 4 | Classical Michaelis-Menten
V = Etot.S.Kcat/Km+S | Substrate
ATP
Product
cAMP
| | The Vmax is scaled down to 7/sec from the Gs-stimulated form. This is constrained because we have a measure of basal activity due to basal phosphorylation by PKC. Two papers measure activation of AC2 by phosphorylation without Gs: Jacobowitz et al JBC 268(6):3829-3832 (Stim 3x) and Yoshimura and Cooper 1993 JBC 26(7):4604-4607 (Stim 9x). The conditions are somewhat different in the two cases. The reference maximally stimulated Vmax is 18/sec from Smigel 1986 JBC 261(4):1976-1982 who has 8.27 umol/min/mg with forskolin stimulated AC. Tang et al JBC 266(13):8595-8603 have an almost identical Vmax of 8 umol/min/mg. This comes to a Vmax of 18/sec. The Km is pretty immaterial since the vast excess of ATP means that the enzyme will normally be saturated. This is a pretty fast enzyme. Note that the saturation of the enzyme means that the regulatory reactions have to involve the complex rather than the free enzyme. |
AC2* acting as a Product of an Enzyme in Synaptic_Network Network
Enzyme Molecule /
Enzyme Activity | Accession Name | Pathway Name | Km (uM) | kcat (s^-1) | Ratio | Enzyme Type | Reagents | PKC-active /
phosph-AC2 | Synaptic_
Network
Accession No. : 16 | Shared_Object_
Synaptic_
Network
Pathway No. : 70 | 33.3333 | 4 | 4 | explicit E-S complex | Substrate
AC2
Product
AC2*
| | Phorbol esters have little effect on AC1 or on the Gs-stimulation of AC2. So in this model we are only dealing with the increase in basal activation of AC2 induced by PKC k1 = 1.66e-6 k2 = 16 k3 =4 |
AC2* 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. |
| | Name | Accession Name | Pathway Name | Kf | Kb | Kd | tau | Reagents | | 1 | dephosph-AC2 | Synaptic_
Network
Accession No. : 16 | AC
Pathway No. : 85 | 0.1
(s^-1) | 0
(s^-1) | - | - | Substrate
AC2*
Product
AC2
| | | Rate constrained by balancing levels of phosphorylated form, especially given resting PKC levels. | | 2 | Gs-bind-AC2* | Synaptic_
Network
Accession No. : 16 | AC
Pathway No. : 85 | 833.28
(uM^-1 s^-1) | 1
(s^-1) | Kd(bf) = 0.0012(uM) | - | Substrate
AC2*
Gs-alpha
Product
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. |
| Database compilation and code copyright (C) 2022, Upinder S. Bhalla and NCBS/TIFR
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