Figure 3
From: Modeling Neisseria meningitidis metabolism: from genome to metabolic fluxes
Oxidation of cysteine to cystine. Cysteine (CYS) is oxidized to cystine (CYST), forming reactive oxygen O2- (step 1), which can reduce cytochrome c (step 4). The electron is used by cytochrome cbb3, which reduces oxygen to water and causes the concomitant generation of a protonmotive force, ΔμH+ (step 5). The protonmotive force is in turn used to form ATP (step 6). Step 2 involves the formation of hydrogen peroxide (H2O2) from O2- by superoxide dismutase followed by catalase to regenerate oxygen (step 3). Cysteine can be converted to glutathione (GSH), via glutamate-cysteine ligase and glutathione synthetase (step 8). In turn, GSH can be converted to cysteine via gamma-glutamyltranspeptidase and aminopeptidase N (step 9), yielding a functional γ-glutamyl cycle. GSH can be oxidized to glutathione disulfide (GSSG), by glutathione peroxidase (step 7).