title: Enzyme diversity and mosaic gene organization in denitrification.
abstract: Denitrification is a main branch of the global nitrogen cycle. In the past ten years unravelling the underlying biochemistry and genetics has proceeded at an increasing pace. Fungal denitrification has become a new field. The biochemical investigation of denitrification has culminated in the description of the crystal structures of the two types of nitrite reductases. The N2O reductase shares with cytochrome c oxidase the CuA center as a structurally novel metal site. The cytochrome b subunit of NO reductase has a striking conservation of heme-binding transmembrane segments versus the subunit I of cytochrome c oxidase. Another putative denitrification gene product shows structural relation to the subunit III of the oxidase. N2O reductase and NO reductase may be ancestors of energy-conserving enzymes of the heme-copper oxidase superfamily. More than 30 genes for denitrification are located in a > 30-kb cluster in Pseudomonas stutzeri, and comparable gene clusters have been identified in Pseudomonas aeruginosa and Paracoccus denitrificans. Genes necessary for nitrite reduction and NO reduction have a mosaic arrangement with very few conserved locations within these clusters and relative to each other.
authors.affiliation: Lehrstuhl für Mikrobiologie, Universität Fridericiana, Karlsruhe, Germany.
authors.forename: W G
authors.initials: WG
authors.lastname: Zumft
authors.forename: H
authors.initials: H
authors.lastname: Körner
mesh_terms: D000595:Amino Acid Sequence; D004789:Enzyme Activation; D005798:Genes, Bacterial; D006088:Gram-Negative Aerobic Bacteria / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D009572:Nitrite Reductases / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D009876:Operon; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D009569:Nitric Oxide; D010088:Oxidoreductases; D009565:Nitrate Reductases; D009572:Nitrite Reductases; C022763:nitrous oxide reductase; C034747:nitric-oxide reductase; D050901:Nitrate Reductase; D009584:Nitrogen