Athel wrote:
This is a reply to Yalamanchili & Bhala, who asked: <
>Isn't it true that under "normal conditions, the physiologic conc. of <
most intracellular substrates is around the Km of the enzyme? <
Anyway, to return to Yalamanchili & Bhala, how do we know whether it's <
true or not? Maybe it's true, and maybe it isn't, but if you check most <
of the 'evidence' you'll find it involves circular arguments, and the <
last time I checked there were very few intracellular concentrations <
that had actually been measured. Admittedly, this was around 20 years <
ago (in the context of my paper in J. Mol. Biol. 201, 1 (1976)), and <
with the advent of non-invasive methods like NMR there's probably a lot <
more information now. Nonetheless, statements like that of Yalamanchili <
& Bhala were widely made then and indeed much earlier, and I suspect a <
lot of it is just constant repetition of something that has hardly ever <
been seriously questioned.
Does anyone *know* if the generalization is true? <
Knowing if it is true is an experimental problem, but, on the other hand,
MCA should try to predict what would be the consequences if the
concentrations are 1) around the Km 2) very low 3) saturating
4) mixed. I feel that there might be very interesting differences in the
properties of the respective pathways or cycles, but am not competent to
develop the idea. Are there such studies?
Pentcho
