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Reaction List for pathway PKA (Pathway Number 196) |
| 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 | Kf | Kb | Kd | tau | Substrate | Product | |
| 1 | cAMP-bind-site-A 1 | 75 (uM^-1 s^-1) | 110 (s^-1) | Kd(bf) = 1.4667(uM) | - | cAMP2.R2C2 cAMP | cAMP3.R2C2 |
| 2 | cAMP-bind-site-A 2 | 75 (uM^-1 s^-1) | 32.5 (s^-1) | Kd(bf) = 0.4333(uM) | - | cAMP cAMP3.R2C2 | cAMP4.R2C2 |
| 3 | cAMP-bind-site-B 1 | 54 (uM^-1 s^-1) | 33 (s^-1) | Kd(bf) = 0.6111(uM) | - | R2C2 cAMP | cAMP.R2C2 |
| Hasler et al (1992 jun) FASEB J. 6(9):2735-41 say Kd =1e-7M for type II, 5.6e-8 M for type I. Take mean which comes to 2e-13 #/cell Smith et al (1981 Mar) Proc Natl Acad Sci U S A 78(3) 1591-1595 have better data. First kf/kb=2.1e7/M = 3.5e-5 (#/cell).Ogreid and Doskeland (1981 Jul 6) FEBS Lett 129(2) 287-292 have figs suggesting time course of complete assoc is < 1 min. | |||||||
| 4 | cAMP-bind-site-B 2 | 54 (uM^-1 s^-1) | 33 (s^-1) | Kd(bf) = 0.6111(uM) | - | cAMP.R2C2 cAMP | cAMP2.R2C2 |
| For now let us set this to the same Km (1e-7M) as site B. This gives kf/kb = .7e-7M * 1e6 / (6e5^2) : 1/(6e5^2) = 2e-13:2.77e-12 Smith et al (1981 Mar) Proc Natl Acad Sci U S A 78(3) 1591-1595 have better values. They say that this is cooperative, so the consts are now kf/kb =8.3e-4 | |||||||
| 5 | inhib-PKA | 60 (uM^-1 s^-1) | 1 (s^-1) | Kd(bf) = 0.0167(uM) | - | PKA-active PKA-inhibitor | inhibited-PKA |
| This has to be set to zero for matching the expts in vitro. In vivo we need to consider the inhibition though. | |||||||
| 6 | Release-C1 | 60 (s^-1) | 18 (uM^-1 s^-1) | Kd(cb) = 0.3(uM) | - | cAMP4.R2C2 | PKA-active cAMP4.R2C |
| This has to be fast, as the activation of PKA by cAMP is also fast. kf was 10 | |||||||
| 7 | Release-C2 | 60 (s^-1) | 18 (uM^-1 s^-1) | Kd(cb) = 0.3(uM) | - | cAMP4.R2C | PKA-active cAMP4.R2 |
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