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Bistability in Coupled Open Substrate Cycles: Numerical and Experimental Approaches
The dynamic and steady-state behaviors of two open substrate cycles sharing a common interconversion enzyme are investigated in a homogeneous flow-through reactor. Lactate dehydrogenase (LDH) converts pyruvate and NADH into lactate and NAD, respectively. In turn, NAD (+ formate) is recycled into NAD...
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Published in: | Journal of physical chemistry (1952) 1996-12, Vol.100 (49), p.19148-19152 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The dynamic and steady-state behaviors of two open substrate cycles sharing a common interconversion enzyme are investigated in a homogeneous flow-through reactor. Lactate dehydrogenase (LDH) converts pyruvate and NADH into lactate and NAD, respectively. In turn, NAD (+ formate) is recycled into NADH (+ CO2) by formate dehydrogenase (FDH), and in the presence of the oxidized form of 2-(hydroxymethyl)-6-methoxy-1,4-benzoquinone (Q), lactate is reoxidized into pyruvate (+ Qred) by flavocytochrome b 2 (FCytb2). When operating under thermodynamically open conditions by a continuous supply of pyruvate, quinone, NADH, and formate, this multienzyme system can exhibit multiple steady states under the form of dynamic hysteresis when using, among others, the pyruvate input concentration as the control parameter. This nonlinear behavior results from the strong inhibition of LDH exerted by its substrate pyruvate. The numerical predictions of a simple mathematical model, taking into account the coupling between the actual enzyme rate equations and mass transfers, agree both quantitatively and qualitatively with the observed experiments. |
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ISSN: | 0022-3654 1541-5740 |
DOI: | 10.1021/jp961734u |