Nitrate reductase

Nitrate reductase enzymes are a group of enzymes which reduce nitrate to nitrite.


 * Nitrate reductase (1)- is a large and complex enzyme ; has multiple subunits and ~ 800 kD. Contains bound FAD, Mo, and cytochrome 557 and has ferredoxin Fe4S4 center. It is NADH/NADPH-dependent according to organism. Mo is bound to a cofactor containing a pteridine ring to form molybdopterin.


 * Nitrite reductase (2, 3, 4) catalyzes the last three steps in the reduction of nitrate to NH3. Contains one ferredoxin Fe2S2 center and one molecule of siroheme (partially reduced Fe porphyrin) and the electron donor for each step is ferredoxin.