   1.7.2.2 | NH3 + 2 H2O + 6 ferricytochrome c = nitrite + 6 ferrocytochrome c + 7 H+ |
reaction mechanism, overview. NO2- binds to the enzyme ccNIR catalytic heme in the Fe2+ state, accepts two protons, and releases H2O to form a moiety formally written as Fe(II)-[NO+]. The key mechanistic challenge in reducing NO2- is to avoid or overcome formation of the terminal Fe(II)-NO thermodynamic sink through one-electron reduction of Fe(II)-[NO+]. Enzyme ccNIR achieves this by two proton-coupled electron transfer reductions that promptly reduce Fe(II)-[NO+] to Fe(II)-[HNO]. The process involves recharging of the catalytic heme with electrons obtained through transfer from the other hemes of the enzyme and of the heme environment with protons |
742740 |
