Nitrate and nitrite, metabolism

The iron-sulfur cluster is often present as the prosthetic group in oxidoreductases where the couple of the substrate is below 0 mV. This reflects the reducing power of the iron-sulfur cluster. There are, however, a small number of iron-sulfur-containing enzymes that function in the positive redox range. These are often associated with bacterial nitrate and nitrite metabolism. The least complicated enzymes contain no additional cofactor, while others contain a number of additional cofactors. 

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