Thermodynamic and Probabilistic Metabolic Control Analysis of Riboflavin (Vitamin B₂) Biosynthesis in Bacteria.
In this study, we applied a coupled in silico thermodynamic and probabilistic metabolic control analysis methodology to investigate the control mechanisms of the commercially relevant riboflavin biosynthetic pathway in bacteria. Under the investigated steady-state conditions, we found that several enzyme reactions of the pathway operate far from thermodynamic equilibrium (transformed Gibbs energies of reaction below about -17 kJ mol(-1)). Using the obtained thermodynamic information and applying enzyme elasticity sampling, we calculated the distributions of the scaled concentration control coefficients (CCCs) and scaled flux control coefficients (FCCs). From the statistical analysis of the calculated distributions, we inferred that the control over the riboflavin producing flux is shared among several enzyme activities and mostly resides in the initial reactions of the pathway. More precisely, the guanosine triphosphate (GTP) cyclohydrolase II activity, and therefore the bifunctional RibA protein of Bacillus subtilis because it catalyzes this activity, appears to mainly control the riboflavin producing flux (mean FCCs = 0.45 and 0.55, respectively). The GTP cyclohydrolase II activity and RibA also exert a high positive control over the riboflavin concentration (mean CCCs = 2.43 and 2.91, respectively). This prediction is consistent with previous findings for microbial riboflavin overproducing strains.
Institute for Chemical Process Engineering, Mannheim University of Applied Sciences, Paul-Wittsack-Straße 10, 68163, Mannheim, Germany. m.birkenmeier@hs-mannheim.de.
Markus
M
Birkenmeier
Institute for Technical Microbiology, Mannheim University of Applied Sciences, Paul-Wittsack-Straße 10, 68163, Mannheim, Germany. m.mack@hs-mannheim.de.
Matthias
M
Mack
Institute for Chemical Process Engineering, Mannheim University of Applied Sciences, Paul-Wittsack-Straße 10, 68163, Mannheim, Germany. t.roeder@hs-mannheim.de.
Thorsten
T
Röder
D001412:Bacillus subtilis / Q000378:metabolism*; D019295:Computational Biology / Q000379:methods*; D011336:Probability; D012256:Riboflavin / Q000096:biosynthesis*; D013816:Thermodynamics
D012256:Riboflavin
In silico pathway analysis; Limiting reactions/enzymes; Metabolic control analysis; Monte Carlo simulation; Probabilistic predictions; Random sampling; Riboflavin/vitamin B2 biosynthesis; Thermodynamic analysis; Uncertainty modeling