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Figure 2 | Microbial Cell Factories

Figure 2

From: Systems biology of lactic acid bacteria: a critical review

Figure 2

Illustration of the difference between measuring flux in systems without and with regulatory constraints. The flux in a pathway with two irreversible Michaelis-Menten enzymes was calculated. The amount of the first enzyme e1 was varied either independently of e2, as it should be to measure its control coefficient, or in a system in which the total amount of enzyme e1 + e2 is constrained. In the latter system an optimal distribution of the enzymes is observed at e1 = 0.4. In the neighborhood of that optimum e1 has no apparent control on the flux (nor does e2). Rate equations and parameter values used: v1 = k1e1(S / K S )/(1 + (S / K S ) + (X / K S K IX ))v2 = k2e2X / (K X + X) k1 = 2, k2 = 1, K S = 1, K IX = 5, K X = 2, and S = 5.

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