Abstract
To improve metabolic pathways for enhancement of a targeted product systematically, quantitative systems analysis in bionetworks of gene, protein, and metabolic pathways is highly desired. Quantification of effect of perturbation of genes and proteins on metabolic fluxes enables to elucidate the parameters responsible for the control of flux in metabolic pathways. In this study, mechanism of flux redistribution at a key branch point in glutamate production by coryneform bacteria, Corynebacterium glutamicum and Corynebacterium efficiens is studied. The quantitative analysis at a key branch point, namely, 2-oxoglutarate(αKG), was performed by comparison of flux distribution before and after addition of the triggering operations such as depletion of biotin and addition of Tween 40. The flux redistribution from the central pathway to glutamate synthetic pathway obviously occurred after the decrease in activity of 2-oxoglutarate dehydrogenase complex, ODHC, while activities of other enzymes at the branch point of isocitrate dehydrogenase, ICDH, and glutamate dehydrogenase, GDH, were not significantly changed. The comparative studies on flux distribution of a wild type strain of C. glutamicum and two genetically engineered strains which harbor a plasmid with genes encoding ICDH and GDH, respectively, also reached the same conclusion that the ODHC is the most crucial factor for the control of flux distribution at the 2-oxoglutarate branch point. The difference in glutamate production between C. glutamicum and C. efficiens is due to a result of the difference in the degree of decrease in ODHC activity. A model with kinetic parameters well explained the phenomena of flux redistribution at the 2-oxoglutarate branch point and predicted flux redistribution.
