Structure and function of periplasmic nitrate reductase.

Nitrate reductases are molybdenum cofactor (Moco)-containing enzymes that reduce nitrate to nitrite, the first step in assimilatory and dissimilatory nitrate reduction to ammonia, and in denitrification. Nitrate reductases are divided into four groups; this review will focus on periplasmic nitrate reductase (Nap), discussing the available structures of NapA in the context of other members of the DMSO reductase family. The mechanism and the roles of a specific amino acid residue are also discussed.