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
