Nitrite Reductase

The ability to reduce nitrate (NO 3-) to ammonia (NH 3) is common to virtually all plants, fungi, and bacteria. It occurs in the following four steps:

> NO 3- -> NO 2- -> NO- -> NH 2 OH -> NH 3.

The first step, conversion of NO 3- to NO 2-, is catalyzed by a large and complex enzyme called nitrate reductase.

The last three steps in the reduction of nitrate to ammonia are carried out by nitrite reductase. It contains one Fe 2S 2 center and one molecule of siroheme, a partially reduced iron porphyrin. The electron donor for each step is ferredoxin.

See also: The Nitrogen Cycle, Nitrogen Fixation, Utilization of Ammonia, , Dimethylsulfoxide Reductase

INTERNET LINK: Nitrate Uptake and Reduction