From owner-metabolic-reg@net.bio.net Tue Jan 25 22:00:00 1994
Path: biosci!daresbury!not-for-mail
From: SCHLOSSER@ciit.org (Paul Schlosser)
Newsgroups: bionet.metabolic-reg
Subject: re: MCA
Date: 26 Jan 1994 14:12:41 -0000
Lines: 36
Sender: daemon@mserv1.dl.ac.uk
Distribution: bionet
Message-ID: <2i5top$e7l@mserv1.dl.ac.uk>
Original-To: btk-mca@net.bio.net

In <9401251925.AA14413@net.bio.net>
noronha@coe1.engr.umbc.edu (Santosh Noronha) writes:

>I propose to calculate response coefficients
>based  solely on flux data ( from end product vs time profiles) and inhibitor
>kinetics. 

If the rate of a step depends on the concentration of an intermediate pool,
which is subject to change, then you need to account for that effect by
measuring, or at least modeling, the concentration.  You can't do this
based solely on flux data since that doesn't tell you what the elasticities
are.  If you have an inhibitor specific to one enzyme, then you can use that
to measure the coefficient of the enzyme directly (assuming that you know the
% inhibition caused by x amount of inhibitor.)

For example if you have  A -E1-> B -E2-> C
and you have no way of measuring or estimating [B], and do not know the
elasticities of E1 and E2 w.r.t. B, then you cannot determine the separate
coefficients of the flux w.r.t. E1 and E2, only the sum of the two, which is
1 in this case.

>However i am not too clear as to how i would be able to isolate the
>effects of an inhibitor on a particular step when the enzymes involved handle
>multiple steps.

Does the inhibitor effect all reactions of the enzyme or only specific ones?
If it inhibits all reactions, then you cannot, and it makes no sense to,
isolate the effect.  I assume that what you want to know is "If I increase
the activity of Enzyme i by 1%, what changes occur in the fluxes?"  Since
increasing i will directly effect the rate of all the steps it catalyzes,
it does not seem meaningful to consider an increase in only one of those
steps.

Paul
schlosser@beta.ciio.org


.