Copper nitrite

The blue protein from A. faecalis strain S-6, which was isolated as a requirement for transferring electrons to a copper-containing nitrite reductase, has since been shown to have sequence homology with proteins arbitrarily designated pseudoazurin by Ambler and Tobari (1985), from Achromobacter cycloclastes and from Pseudomonas AMI. [Pseudomonas AMI also produces amicyanin, which is the recipient of electrons from methylamine dehydrogenase, (see below)]. In A. cycloclastes reduced pseudoazurin donates electrons to a copper nitrite reductase (Liu et ai, 1986), as it does in A. faecalis. Ambler and Tobari (1985)... 

Coyne, M. S., Arunakumari, A., Averill, B. A., and Tiedje, J. M. (1989). Immunological identification and distribution of dissimilatory heme cd, and nonheme copper nitrite reductases in denitrifying bacteria. Appl. Environ. Microbiol. 55, 2924-2931. 

Shapleigh, J. P., and Payne, W. J. (1985a). Differentiation of cd, cytochrome and copper nitrite reductase production in denitrifiers. FEMS Microbiol. Lett. 26, 275-279. 

Tolman, W. B. (1991). A model for the substrate adduct of copper nitrite reductase and its conversion to a novel tetrahedral copper(ll) triflate complex. Inorg. Chem. 30, 4877-4880. 

The sensitivity of AN to initiation by heat may be increased or decreased by the presence of certain inorganic impurities. For instance, small amts of Cu increase sensitivity to heat because of the formation of a small amt of copper nitrite, which causes instability (Ref 90). The formation of Cu nitrite also was reported in Mellor, v 7 (Ref 16). Mellor also reports that the presence of Fe, Al or especially Zn in powdered form lowers the temperature required for the decompn of AN. Kast (Ref 31) reported that the presence of KMn04 in powdered form may cause the spontaneous heating of AN. Investigations conducted at Pic Arsn showed that different Cr compds such as the oxide and nitrate catalyze the decompn of AN, and in some cases explosions occurred at temps as low as 200°. Among the inorganic substances which lessen the sensitivity of AN to heat are clay, kiesel-guhr, powdered limestone etc. The same effect was expected of Amm sulfate until the disaster at Oppau in 1921 (Refs 15a 15b) rendered the safety of such a mixt uncertain. Amm sulfate had been used for many years as a desensitizer for AN in fertilizers and it was considered that such mixts could not be... 

Recently several new active site model compounds have been prepared (Carrier et al., 1991) using sterically hindered tris(pyrazoyI)hydroborate (L) and tris(thioethyl)amine (L2) as ligands. The copper nitrite complex LCu11 (N02) models the enzyme substrate complex and X-ray studies confirm that the complex is tetrahedral. A mononuclear copper—nitrosyl complex similar to postulated NO adducts of copper proteins has also been prepared from LCu1 (MeCN) and NO, which has been tentatively identified as a Cu11 -NO species on the basis of IR (v NO 1711 cm 1) and ESR evidence. 

Dodd, F. E., van Beeumen, J., Eady, R. R., and Hasnain, S. S., 1998, X-ray structure of a blue copper nitrite reductase in two crystal forms. The nature of the copper sites, mode of substrate binding and recognition by redox partner, J. Mol. Biol. 282 3699382. 

Figure 2 The dissimilatory denitrification pathway. NO3 is reduced to NO2 by a membrane-bound or periplasmic nitrate reductase(NaR). N02 is reduced to NO by either a cytochrome cdi or copper nitrite reductase (NiR). NO is reduced to N2O by nitric oxide reductase (NOR). N2O is reduced to N2 by nitrous oxide reductase (N2OR). Electron transport from uhiquinol (UQH2) at NaR and the cyt hcj complex is coupled to generation of a proton gradient...

---