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reverse patchclamp?

Pedro Mendes prm at aber.ac.uk
Thu May 5 06:25:23 EST 1994


In article <2qa8ia$9u0 at mserv1.dl.ac.uk> 
Jannie Hofmeyr <jhsh at maties.sun.ac.za> writes:
>
>I am not too sure about this use of pathclamping, but if by some means one 
>could infuse DHAP into a cell to hike up the internal concentration by a 
>factor of ten **and then left the cell to its own devices**, the answer would
>be that on balance nothing would probably happen. DHAP is an intermediate, 
>a metabolic variable; its steady-state concentration is dependent on the 
>values of all the metabolic parameters and as long as the parameters remain 
>the same the long term behaviour of the system is to return to the same 
>steady state. Certainly the system will be pushed into a transient phase, but
>the final state would be the same as the original state.

Unless the ten-fold increase in DHAP was enough to push the system into 
a different  basin of attraction... There are many examples of in vitro and in 
vivo systems in which this can happen (I'm thinking of e.g. peroxidase and
glucose-6-phosphate dehydrogenase, see refs below). So it is a hypothesis that 
we cannot exclude a priori.

References:

Degn, H. (1968) "Bistability caused by substrate inhibition of peroxidase in 
an open reaction system." Nature 217, 1047-1050.

Aon, M.A., Cortassa, S., Hervagault, J.F., and Thomas, D.  (1989), "Ph-induced 
bistable dynamic behavior in the reaction catalyzed by 
glucose-6-phosphate-dehydrogenase and conformational hysteresis of the 
enzyme", Biochem. J.  262, 795-800.


Pedro Mendes
prm at aber.ac.uk



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