Figure 4 . Effect of the flux enforcement of threonine deaminase
(THRD) and succinate dehydrogenase (SUCD1m) reactions on the optimal
flux distribution for SARS-CoV-2 production. The enforced flux
boundaries were [8.94; 9.14] and [-0.58; 8.60]
mmol∙gDW-1∙h-1 for THRD and SUCD1m
respectively. (A) Distribution of the producing (‘in’) and
consuming (‘out’) fluxes for arginine and isoleucine in the cytosol and
succinate in the mitochondrial matrix. For each metabolite, the in and
out fluxes have been computed in four different conditions; from left to
right; unmodified model, flux enforcement of SUCD1m only, flux
enforcement of THRD only, and flux enforcement of both SUCD1m and THRD.
On the succinate panel, the dashed blue line corresponds to the upper
boundaries to which SUCD1m is enforced (8.60
mmol∙gDW-1∙h-1). (B)Cartoon representation of the reaction network involving threonine and
other metabolites, with reaction fluxes from normal and perturbation
conditions colour-mapped onto reaction arrows. Metabolite notations used
are: 2-oxobutanoate (2obut), 3-methyl-2-oxobutanoate (3mob),
4-methyl-2-oxopentanoate (4mop), and alpha-keto-glutarate
(akg).