Dissimilatory sulfite reductases (dSiRs) are crucial enzymes in bacterial sulfur-based energy metabolism, which are likely to have been present in some of the earliest life forms on Earth. Several classes of dSiRs have been proposed on the basis of different biochemical and spectroscopic properties, but it is not clear whether this corresponds to actual physiological or structural differences. ...

Thiobacillus thiooxidans cells oxidized elemental sulfur to sulfite, with 1 mol of O(2) consumption per mol of sulfur oxidized to sulfite, when the oxidation of sulfite was inhibited with 2-n-heptyl-4-hydroxyquinoline N-oxide.

In phototrophic sulfur bacteria, sulfite is a well-established intermediate during reduced sulfur compound oxidation. Sulfite is generated in the cytoplasm by the reverse-acting dissimilatory sulfite reductase DsrAB. Many purple sulfur bacteria can even use externally available sulfite as a photosynthetic electron donor. Nevertheless, the exact mode of sulfite oxidation in these organisms is a ...

The biochemical basis for sulfite accumulation by sulfate-using revertants of Salmonella pullorum was determined. All of the sulfate-using mutants isolated from wild-type S. pullorum accumulated sulfite when grown at 37 but not at 25 C. The specific activity of reduced nicotinamide adenine dinucleotide (NADPH)-dependent sulfite reductase (H2S-NADP oxidoreductase, EC 1.8.1.2) and of reduced meth...

The rate of oxygen uptake of spinach ferredoxin-NADP reductase-ferredoxin complex is increased up to ZO-fold by the addition of cytochrome c. Initiation of epinephrine and sulfite oxidation indicated an involvement of the superoxide anion radical in the stimulated oxidase reaction. The final product of the reaction was shown to be Hz0 instead of HsOt, which is the product of the flavoprotein-ca...

The properties of a ferric ion-reducing system which catalyzes the reduction of ferric ion with elemental sulfur was investigated with a pure strain of Thiobacillus ferrooxidans. In anaerobic conditions, washed intact cells of the strain reduced 6 mol of Fe with 1 mol of elemental sulfur to give 6 mol of Fe, 1 mol of sulfate, and a small amount of sulfite. In aerobic conditions, the 6 mol of Fe...

Urocanase is inactivated in vivo and is reactivated by ultraviolet radiation. The chemistry of this photoregulation of urocanase was studied. Purified enzyme was inactivated by 25 pM sulfite (tl,z, 15 min). Dialyzed sulfite-treated inactive enzyme was photoactivatable. The activity can be cycled repeatedly by alternate ultraviolet light and sulfite treatments. Active enzyme binds 5 times more [...