Pseudomonas aeruginosa cytochrome nitrite reductase

Akey, C. E., Moffat, K., Wharton, D. C., and Edelstein, S. j. (1980). Characterization of crystals of a cytochrome oxidase (nitrite reductase) from Pseudomonas aeruginosa by X-ray diffraction and electron microscopy. . Mol. Biol. 136, 19-43. 

Direct electrochemistry has also been used (72-78) to couple the electrode reactions to enzymes for which the redox proteins act as cofactors. In the studies, the chemically reduced or oxidized enzyme was turned over through the use of a protein and its electrode reaction as the source or sink of electrons. In the first report (72, 73) of such application, the electrochemical reduction of horse heart cjd,ochrome c was coupled to the reduction of dioxygen in the presence of Pseudomonas aeruginosa nitrite reductase/cytochrome oxidase via the redox proteins, azurin and cytochrome C551. The system corresponded to an oxygen electrode in which the four-electron reduction of dioxygen was achieved relatively fast at pH 7. 

Yamanaka and co-workers (364-366) have crystallized a cytochrome oxidase from P. aeruginosa which oxidizes Pseudomonas ferrocytochrome c-551. It is also capable of nitrite reduction with a turnover number of 4000 moles nitrite reduced under anaerobic conditions to nitric oxide per minute at 37°. It is an adaptive enzyme, nitrate being essential for its biosynthesis. The enzyme has a molecular weight of 120,000, with two subunits of equivalent molecular weight, 2 heme c and 2 heme d groups per mole (Fig. 38) (366a). Nitrite reductase activity is 94% inhibited by 8 X 10 M KCN, but only by CO. The lack of CO inhibition appears to be related to the fact that the enzyme has a greater affinity for nitrite than for carbon monoxide. 

Cytochrome c-552 belongs to cytochrome c6 or c8 group. As the cytochromes of this group react rapidly with Pseudomonas aeruginosa nitrite reductase but does not react with cow cytochrome c oxidase (Yamanaka, 1992), their structures have been supposed to be similar to each other. Thus, their amino acid sequences resemble each other though the sequence of Chlorobium limicola f. thiosulfatophi-lum cytochrome c-555 shows smaller similarity to other cytochromes c6 or c8 than the similarities that other cytochromes c6 or c8 show each other (Table 3.2). 

Nagata Y, Yamanaka T, Okunuki K (1970) Amino acid composition and iV-terminus of Pseudomonas cytochrome oxidase (= Pseudomonas aeruginosa nitrite reductase). Biochim Biophys Acta 221 668-671... 

Nitrite reduction to nitric oxide is catalyzed by dissimilatory nitrite reductase. The enzymes purified from Alcaligenes faecalis (Iwasaki and Matsub-ara, 1971), Pseudomonas aeruginosa (Walker and Nicholas, 1961), andMj-crococcus denitrificans (Newton, 1969) have been shown to contain c d-type cytochrome. The nitrite reductase from Achromobacter cycloclastes does not... 

Heme di (107), which was isolated by Timkovich et al (70) and Chang et al (71) occurs as one of two cofactors in the reductase cytochrome cd. Cytochrome cd participates in the reduction of nitrite to nitrous oxide (N2O) in chemoautotrophic bacteria, such as Pseudomonas aeruginosa, Paracoccus denitrificans, and Thiobacillus denitrificans (13). From recent investigations it seems very likely that cytochrome cdi mediates the nitrite reduction to nitric oxide (NO) and that a second enzyme produces N2O from NO (13). A structure was... 

SUvestrini, M.C., S. FalcineUi, 1. Ciabatti, F. Culruzzola, and M. Brunori (1994). Pseudomonas aeruginosa nitrite reductase (or cytochrome oxidase) An overview. Biochimie 76, 641-654. 

Lojou, E., F. Cutruzzola, M. Tegoni, and P. Bianco (2003). Electrochemical study of the intermolecular electron transfer to Pseudomonas aeruginosa cytochrome cd nitrite reductase. Electrochim. Acta 48, 1055-1064. 

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