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Fig. 1 | BMC Systems Biology

Fig. 1

From: Tracing regulatory routes in metabolism using generalised supply-demand analysis

Fig. 1

An example of generalised supply-demand analysis of three metabolic systems. a An example of a simple linear pathway partitioned into supply and demand blocks around intermediate P. b A rate characteristic plot that shows how the fluxes local to the supply and demand blocks of P respond to a change in p over a large concentration range. The vertical dotted line indicates the steady-state concentration of P (\(\bar {p}\)), while the steady-state flux of the system as a whole obtains where the rates of the supply and demand blocks intersect. Elasticity coefficients of the reactions in the supply and demand blocks that interact directly with P (reactions 2 and 3 respectively) are indicated with solid lines while response coefficients of the blocks towards p are indicated by dashed lines. c The pathway in (a) with the addition of allosteric inhibition of enzyme 1 by P, which creates an additional direct route of interaction between P and its supply block via reaction 1. d The rate characteristic plot for the supply and demand blocks of the intermediate P in (c). e The pathway in (a) with the addition of allosteric inhibition of enzyme 1 by S 2, which creates an indirect route of interaction between P and its supply block via reaction 3. f The rate characteristic plot for the supply and demand blocks of the intermediate P in (e). In (d) and (f) only the total and partial response coefficients of the supply block towards p are shown and the slopes of the partial response coefficients (solid lines) add up to that of the total response coefficient (dashed line)

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