Sulfite reductant

The procedure given above for the preparation of methanesulfonyl cyanide essentially is a combination of the sulfite reduction of a sulfonyl... 

Sulfite reductase catalyzes the six-electron reduction by NADPH of sol" to and NO2 to NH3. In E. coli this enzyme is a complex structure with subunit composition 0 8)84 (Siegel et al, 1982). The enzyme active site is on the /3 subunit, which contains both a 4Fe 4S cluster and a siroheme prophyrin. Substrates and ligands have been found to bind to the siroheme. The a subunit binds NADPH and serves to shuttle electrons to the active site through bound FAD and FMN groups. Isolated )8 subunits can catalyze sulfite reduction in the presence of a suitable electron donor. 

The sulfonic acids of these metallocenes can be converted to sulfonyl chlorides, sulfonamides, etc., by appropriate reagents. Reduction of ferrocene-sulfonyl chloride by lithium aluminum hydride produces the rapidly oxidized ferrocenethiol in quantitative yield (43). Both the sulfonic acid of cyclopentadienylmanganese tricarbonyl and the corresponding sulfinic acid (obtained by sodium sulfite reduction of the sulfonic acid) have been converted to sulfones (10). 

Sulfite reduction of diazonium salts leads to hydrazines. 

Stannous chloride or sodium sulfite reduction to the hydrazine from which the hydrocarbon is obtained by oxidation.7... 

Also reactions with quiones and a -unsaturated compounds. b Enzymic sulfate and sulfite reductions reductant requirement equivalent to 4NADPH + 4H+. 

Bisulfite addition to pyrimidines Disulfide cleavage Sulfite oxidation Sulfite reduction... 

Akagi, J. M. The participation of a ferredoxin of Clostridium nigrifieans in sulfite reduction. Biochem. Biophys. Res. Commun. 21, 72—77 (1965). 

Table I also shows the great diversity of organisms in which iron—sulfur proteins have been detected. Thus far there is no organism which when appropriately examined has not contained an iron-sulfur protein, either in the soluble or membrane-bound form. Iron-sulfur proteins catalyze reactions of physiological importance in obligate anaerobic bacteria, such as hydrogen uptake and evolution, ATP formation, pyruvate metabolism, nitrogen fixation, and photosynthetic electron transport. These properties and reactions can be considered primitive and thus make iron-sulfur proteins a good place to start the study of evolution. These key reactions are also important in higher organisms. Other reactions catalyzed by iron-sulfur proteins can be added such as hydroxylation, nitrate and nitrite reduction, sulfite reduction, NADH oxidation, xanthine oxidation, and many other reactions (Table II).

Yoshimoto and Sato (4 1) have isolated sulfite reductases from four mutants of sulfite reduction by NADPH, but could utilize MVH as electron donor. All the mutant enzymes contained the chromophore responsible for the 386- and 587-nm peaks, nonheme iron, and labile sulfide. Three of these mutant enzymes contained FMN no flavin was detected in the fourth. The sedimentation coefficients of these preparations... 

These conclusions regarding the yeast sulfite reductase are essentially in agreement with our current knowledge of the mechanism of sulfite reduction by NADPH and MVH in the E. coli enzyme. 

FIGURE 1. Examples of reactions catalyzed by molybdenum containing enzymes. From top to bottom, hydroxylation of xanthine, hydroxylation of acetaldehyde, dehydrogenation of carbon monoxide, transhydroxylation of pyrogallol, oxidation of sulfite, reduction of nitrate, reduction of dimethylsulfoxide, oxidation of formate, reduction of polysulfide and formation of formylmethanofuran. 

Fitz R. M. and Cypionka H. (1990) Formation of thiosulfate and trithionate during sulfite reduction by washed cells of Desulfovibrio desulfuricans. Arch. Microbiol. 154, 400-406. 

Sulfur isotope fractionation during sulfite reduction and synergistic sulfate... 

Multi-step models of biological sulfate and sulfite reduction. . . 329... 

Jones, H.E. and Skyring, G.W., 1975. Effect of enzymic assay conditions on sulfite reduction catalyzed by desulfoviridin from Desulfovibrio gigas. Biochim. Biophys. Acta, 377 52-60. 

Kobayashi, K., Tachibana, S. and Ishimoto, M., 1969. Intermediary formation of tri-thionate in sulfite reduction by sulfate-reducing bacterium. J. Biochem., Tokyo, 65 155-157. 

Krouse, H.R., McCready, R.G.L., Husain, S.A. and Campbell, J.N., 1968. Sulphur isotope fractionation kinetic studies of sulfite reduction in growing cells of Salmonella Heidelberg. Biophys. J., 8 109—124. 

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