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Lactate formation in Caldicellulosiruptor saccharolyticus is regulated by the energy carriers pyrophosphate and ATP

Paper ID Volume ID Publish Year Pages File Format Full-Text
31879 44847 2010 9 PDF Available
Title
Lactate formation in Caldicellulosiruptor saccharolyticus is regulated by the energy carriers pyrophosphate and ATP
Abstract

Caldicellulosiruptor saccharolyticus displays superior H2 yields on a wide range of carbon sources provided that lactate formation is avoided. Nevertheless, a low lactate flux is initiated as the growth rate declined in the transition to the stationary phase, which coincides with a drastic decrease in the glucose consumption and acetate production fluxes. In addition, the decrease in growth rate was accompanied by a sudden increase and then decrease in NADH levels. The V′MAX of the lactate dehydrogenase (LDH) doubled when the cells entered the stationary phase. Kinetic analysis revealed that at the metabolic level LDH activity is regulated through (i) competitive inhibition by pyrophosphate (PPi, ki=1.7 mM) and NAD (ki=0.43 mM) and (ii) allosteric activation by FBP (300%), ATP (160%) and ADP (140%). From these data a MWC-based model was derived. Simulations with this model could explain the observed lactate shift by displaying how the sensitivity of LDH activity to NADH/NAD ratio varied with different PPi concentrations. Moreover, the activation of LDH by ATP indicates that C. saccharolyticus uses LDH as a means to adjusts its flux of ATP and NADH production. To our knowledge, this is the first time PPi is observed as an effector of LDH.

Keywords
Caldicellulosiruptor saccharolyticus; Lactate dehydrogenase; Pyrophosphate; ATP activation; Allosteric regulation; Enzyme modeling
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Lactate formation in Caldicellulosiruptor saccharolyticus is regulated by the energy carriers pyrophosphate and ATP
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Publisher
Database: Elsevier - ScienceDirect
Journal: Metabolic Engineering - Volume 12, Issue 3, May 2010, Pages 282–290
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
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