| |
Enzyme Molecule /
Enzyme Activity | Pathway Name /
Pathway No. | Km
(uM) | kcat
(s^-1) | Ratio
(k2/k3) | Enzyme Type | Reagents |
| 1 | AC1-CaM /
kenz | AC
Pathway No. 251 | 299.998 | 4.5 | 4 | Classical Michaelis-Menten
V = Etot.S.Kcat/Km+S | Substrate:
ATP
Product :
cAMP
|
| | 17 Feb 2005 Halved Vmax as the amount of enzyme has been doubled to get an integer value in the spine. 18 Feb 2005. Updated Km from BRENDA: EC No 4.6.1.1 Rat Km: 0.95 mM Turnover 12/sec. Human Km: 0.3 mM 12 umol/min/mg for mammalia, turnover is 12/sec See PMID 8663304 by Dessauer and Gilman JBC 271 1996 Unfortunately turnover range is from 34 down to 0.1 in different studies, according to BRENDA. |
| 2 | AC2* /
kenz | AC
Pathway No. 251 | 300.002 | 2 | 4 | Classical Michaelis-Menten
V = Etot.S.Kcat/Km+S | Substrate:
ATP
Product :
cAMP
|
| | Reduced Km to match expt data for basal activation of AC2 by PKC. Now k1 = 2.9e-6, k2 = 72, k3 = 18 18 Feb: Raised Km to 300 based on BRENDA data. Unlikely to make much difference, given the vast amount of ATP. |
| 3 | cAMP-PDE /
PDE | AC
Pathway No. 251 | 19.8411 | 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 |
| 4 | cAMP-PDE* /
PDE* | AC
Pathway No. 251 | 19.8413 | 20 | 4 | explicit E-S complex | Substrate:
cAMP
Product :
AMP
|
| | This form has about twice the activity of the unphosphorylated form. See Sette et al JBC 269:28 18271-18274 1994. We'll ignore cGMP effects for now. |
| 5 | PDE1 /
PDE1 | AC
Pathway No. 251 | 39.6999 | 1.667 | 4.0012 | explicit E-S complex | Substrate:
cAMP
Product :
AMP
|
| | Rate is 1/6 of the CaM stim form. We'll just reduce all lf k1, k2, k3 so that the Vmax goes down 1/6. |
| 6 | CaM.PDE1 /
CaM.PDE1 | AC
Pathway No. 251 | 39.6831 | 10 | 4 | explicit E-S complex | Substrate:
cAMP
Product :
AMP
|
| | Max activity ~10umol/min/mg in presence of lots of CaM. Affinity is low, 40 uM. k3 = 10, k2 = 40, k1 = (50/40) / 6e5. |
and 
color.
arrow indicates that ordering is done according to ascending or descending order.