title: Enzymology and molecular biology of prokaryotic sulfite oxidation.
abstract: Despite its toxicity, sulfite plays a key role in oxidative sulfur metabolism and there are even some microorganisms which can use it as sole electron source. Sulfite is the main intermediate in the oxidation of sulfur compounds to sulfate, the major product of most dissimilatory sulfur-oxidizing prokaryotes. Two pathways of sulfite oxidation are known: (1) direct oxidation to sulfate catalyzed by a sulfite:acceptor oxidoreductase, which is thought to be a molybdenum-containing enzyme; (2) indirect oxidation under the involvement of the enzymes adenylylsulfate (APS) reductase and ATP sulfurylase and/or adenylylsulfate:phosphate adenylyltransferase with APS as an intermediate. The latter pathway allows substrate phosphorylation and occurs in the bacterial cytoplasm. Direct oxidation appears to have a wider distribution; however, a redundancy of pathways has been described for diverse photo- or chemotrophic, sulfite-oxidizing prokaryotes. In many pro- and also eukaryotes sulfite is formed as a degradative product from molecules containing sulfur as a heteroatom. In these organisms detoxification of sulfite is generally achieved by direct oxidation to sulfate.
authors.affiliation: School of Molecular and Microbial Sciences, The University of Queensland, St. Lucia, Qld. 4072, Australia. kappler@biosci.uq.edu.au
authors.forename: U
authors.initials: U
authors.lastname: Kappler
authors.forename: C
authors.initials: C
authors.lastname: Dahl
mesh_terms: D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011387:Prokaryotic Cells / Q000201:enzymology / Q000378:metabolism*; D016415:Sequence Alignment; D013430:Sulfate Adenylyltransferase / Q000235:genetics / Q000378:metabolism; D013447:Sulfites / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism
chemical_list: D013447:Sulfites; D013455:Sulfur; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; C019618:adenylylsulfate reductase; D013430:Sulfate Adenylyltransferase