Pseudomonas aeruginosa nitrate reductase

Carlson, C. A., Ferguson, L. P., and Ingraham, J. L. (1982). Properties of dissimilatory nitrate reductase purified from the denitrifier Pseudomonas aeruginosa. J. Bacteriol. 151, 162-171. 

Pseudomonas aeruginosa can synthesize both types of nitrate reductase, depending upon the environmental conditions, the dissimilatory enzyme being repressed by dioxygen.1049... 

At least 12 genes are involved in the formation of nitrate reductase in various Enterobacteriaceae, 5 nar genes have been identified in Pseudomonas aeruginosa and 13 Chi mutations have been characterized in Bacillus licheniformis (Stouthamer, 1976). The physiological properties of chlorate-resistant mutants have been characterized and their location on the circular chromosome determined. Chi mutations have a pleotropic affect such characteristics as dehydrogenase activity, cytochrome distribution, and membrane protein composition may be influenced. The different Cfi/ mutants are able to synthesize various components of the complex nitrate reductase molecule. It is possible, in some instances, to form active enzyme by mixing components extracted from the appropriate mutants (Stouthamer, 1976). 

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. 

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