Fig. 6: The architecture of central carbon metabolism in P. putida enables rapid supply of NADPH upon oxidative stress.

a Schematic representation of the upper metabolism of P. putida KT2440. Several biochemical reaction have been lumped to illustrate the main routes for carbon circulation (see Fig. S1 for details and abbreviations). Note that the total rate of carbon uptake (q_S) is split between glucose phosphorylation and oxidation to gluconate, such that q_S = r_p + r_ox. The overall cycling flux of trioses phosphate towards hexoses phosphate is indicated as r_c and the flux through the PP pathway shunt is termed r_s. Cofactors other than NADPH have been omitted in the drawing for the sake of clarity. b Functional relationship between r_NADPH, the rate of NADPH formation within the simplified metabolic network of (a), and the fluxes through the oxidative loop for glucose processing and the PP pathway shunt. All (arbitrary) values are given as a fraction of q_S, and the experimental conditions tested in this work are indicated with red dots (Ctrl. control conditions). c General model for flux distribution in the upper metabolic domain of P. putida. Under normal growth conditions, glucose is processed mostly through its oxidative conversion to gluconate, and the EDEMP cycle provides intermediates for biomass, with a very low flux through the PP pathway. Upon oxidative stress conditions (exerted either by endogenous or external perturbations), a rapid increase of fluxes via the PP pathway shunt replenishes the intermediates within upper metabolism and provides a direct source of NADPH that can be coupled to anti-oxidant defense mechanisms against reactive oxygen species (ROS). Fluxes predominant under each condition are highlighted.