Nitrate reductase
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Nitrate reductase enzymes are a group of enzymes that reduce nitrate to nitrite.
- Nitrate reductase (1)- is a large and complex enzyme with multiple subunits and a mass of ~800 kDa. It 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. It contains one ferredoxin Fe2S2 center and one molecule of siroheme (partially-reduced Fe porphyrin) and the electron donor for each step is ferredoxin.