Bacterial sulfite dehydrogenase

Wodara, C., Bardischewsky, F., and Friedrich, C. G., 1997, Cloning and characterization of sulfite dehydrogenase, two c-type cytochromes, and a flavoprotein of Paracoccus denitri-ficans GB17 essential role of sulfite dehydrogenase in lithotrophic sulfur oxidation. J. Bacterial. 179 501495023. 

The active site geometries (Figure 2.14) of the sulfite oxidizing enzymes are quite similar and examples of high-resolution X-ray crystal structures can be found for the S. novella sulfite dehydrogenase (bacterial)/ A. thaliana sulfite oxidase (plant)/ bacterial YedY/ and vertebrate sulfite oxidase. ... 

Beef heart preparations allow sulfite to accumulate. In bacterial and liver systems sulfate is the product. (8-Sulfonylpyruvate has been found to be inert in both systems, indicating that the sulfate is formed by oxidation of inorganic sulfite. A partially purified sulfite dehydrogenase has been obtained from liver. This enzyme catalyzes the reduction of methylene blue by sulfite. Similar activities have been found in some bacteria. 

Three human redox enzymes, and a variety of bacterial enzymes, contain molybdenum chelated by two sulfur atoms in a modified pterin molybdopterin (see Figure 10.1). In sulfite oxidase, the other two chelation sites of the molybdenum are occupied by oxygen in xanthine oxidase / dehydrogenase (Section 7.3.7) and aldehyde oxidase, one site is occupied by oxygen and one by sulfur. In some bacterial enzymes, molybdopterin occurs as a guanine dinucleotide rather than free. In others, tungsten rather than molybdopterin is the chelated metal there is no evidence that any mammalian enzymes contain tungsten. 

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