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Molecule Parameter List for cAMP-PDE

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

cAMP-PDE participated as	Molecule	Sum total of	Enzyme	Substrate of an enzyme	Product of an enzyme	Substrate in Reaction	Product in Reaction
No. of occurrences	1	0	1	1	0	0	1

Accession and Pathway Details

Accession Name	Accession No.	Accession Type	Pathway Link
PKA_2003	47	Network	Shared_Object_PKA_2003,  PKA,  AC,   Gs
This model consists of receptor-ligand interaction, G-protein activation, Adenylyl cyclase mediated formation of cAMP and activation of PKA in the neuron. Demonstration programs using this model described in Bhalla US. (2004) Biophys J. 87(2):733-44 to generate a dose-response curve using stochastic calculations are available here.

cAMP-PDE acting as a Molecule in  PKA_2003 Network

Name	Accession Name	Pathway Name	Initial Conc. (uM)	Volume (fL)	Buffered
cAMP-PDE	PKA_2003 Accession No. : 47	AC Pathway No. : 197	0.5	1000	No
The levels of the PDE are not known at this time. However, enough kinetic info and info about steady-state levels of cAMP etc are around to make it possible to estimate this at about 0.5 uM.

cAMP-PDE acting as an Enzyme in  PKA_2003 Network

Enzyme Molecule / Enzyme Activity	Accession Name	Pathway Name	Km (uM)	kcat (s^-1)	Ratio	Enzyme Type	Reagents
cAMP-PDE / PDE	PKA_2003 Accession No. : 47	AC Pathway No. : 197	19.8413	10	4	explicit E-S complex	Substrate cAMP Product AMP
Best rates are from Conti et al Biochem 34 7979-7987 1995. Though these are for the Sertoli cell form, it looks like they carry nicely into alternatively spliced brain form. See Sette et al JBC 269:28 18271-18274 Km ~2 uM, Vmax est ~ 10 umol/min/mg for pure form. Brain protein is 93 kD but this was 67. So k3 ~10, k2 ~40, k1 ~4.2e-6

cAMP-PDE acting as a Substrate for an Enzyme in  PKA_2003 Network

Enzyme Molecule / Enzyme Activity	Accession Name	Pathway Name	Km (uM)	kcat (s^-1)	Ratio	Enzyme Type	Reagents
PKA-active  / phosph-PDE	PKA_2003 Accession No. : 47	Shared_Object_ PKA_2003 Pathway No. : 195	7.5	9	4	explicit E-S complex	Substrate cAMP-PDE Product cAMP-PDE*
See Bramson et al CRC crit rev Biochem 15:2 93-124. The rates there are for peptide substrates and too fast. Scaled down by a factor of 3 as per Cohen et al FEBS Lett 76:182-86 (1977).

cAMP-PDE acting as a Product in a reaction in  PKA_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.

Name	Accession Name	Pathway Name	Kf	Kb	Kd	tau	Reagents
dephosph-PDE	PKA_2003 Accession No. : 47	AC Pathway No. : 197	0.1 (s^-1)	0 (s^-1)	-	-	Substrate cAMP-PDE* Product cAMP-PDE
The rates for this are poorly constrained. In adipocytes (probably a different PDE) the dephosphorylation is complete within 15 min, but there are no intermediate time points so it could be much faster. Identity of phosphatase etc is still unknown.