Nitrate reduction in the periplasm of gram-negative bacteria

Adv Microb Physiol. 2001:45:51-112. doi: 10.1016/s0065-2911(01)45002-8.


In contrast to the bacterial assimilatory and membrane-associated, respiratory nitrate reductases that have been studied for many years, it is only recently that periplasmic nitrate reductases have attracted growing interest. Recent research has shown that these soluble proteins are widely distributed, but vary greatly between species. All of those so far studied include four essential components: the periplasmic molybdoprotein, NapA, which is associated with a small, di-haem cytochrome, NapB; a putative quinol oxidase, NapC; and a possible pathway-specific chaperone, NapD. At least five other components have been found in different species. Other variations between species include the location of the nap genes on chromosomal or extrachromosomal DNA, and the environmental factors that regulate their expression. Despite the relatively small number of bacteria so far screened, striking correlations are beginning to emerge between the organization of the nap genes, the physiology of the host, the conditions under which the nap genes are expressed, and even the fate of nitrite, the product of Nap activity. Evidence is emerging that Nap fulfills a novel role in nitrate scavenging by some pathogenic bacteria.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Gene Expression Regulation, Bacterial
  • Gram-Negative Bacteria / enzymology
  • Gram-Negative Bacteria / metabolism*
  • Models, Chemical
  • Molecular Sequence Data
  • Nitrate Reductases / metabolism*
  • Nitrates / chemistry
  • Nitrates / metabolism*
  • Nitrates / physiology
  • Oxidation-Reduction
  • Periplasm / enzymology
  • Periplasm / metabolism*
  • Sequence Alignment
  • Sequence Homology, Amino Acid


  • Nitrates
  • Nitrate Reductases