MetaCyc Pathway: sulfate reduction I (assimilatory)
Traceable author statement to experimental support

Enzyme View:

Pathway diagram: sulfate reduction I (assimilatory)

This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Superclasses: Degradation/Utilization/AssimilationInorganic Nutrients MetabolismSulfur Compounds MetabolismSulfate Reduction

Some taxa known to possess this pathway include : Bacillus subtilis, Escherichia coli K-12 substr. MG1655, Saccharomyces cerevisiae

Expected Taxonomic Range: Bacteria , Fungi

General Background

Sulfur is an essential nutrient for all life forms. Plants, fungi, and many bacteria reduce inorganic sulfate to sulfide to cover their need for the element. Before the sulfur can be assimilated into biosynthetic pathways it needs to be reduced to hydrogen sulfide. Pathways catalyzing the reduction of sulfate to sulfide for the purpose of incorporation into newly synthesized molecules are called pathways of assimilatory sulfate reduction. In addition, certain organisms can use sulfate as an alternative electron acceptor in the absence of oxygen. Pathways of sulfate reduction for the purpose of energy production are called pathways of dissimilatory sulfate reduction.

The reduction of sulfate to sulfite requires two electrons at a standard redox potential (E0') of -516 mV, which is too high for physiological electron carriers [Thauer77]. The problem is solved by the activation of the sulfate, by forming a mixed anhydride between phosphate and sulfate as in adenosine 5'-phosphosulfate (APS) or 3'-phosphoadenylyl-sulfate (PAPS). This linkage lowers the potential to E0' = -60 mV, which is easilly covered by thiols or pyrimidine nucleotides [Berndt04].

About This Pathway

In many bacteria and lower eukaryotes, assimilatory sulfate reduction proceeds via activation of sulfate to APS by the enzyme sulfate adenylyltransferase (also known as ATP sulfurylase). This enzyme has an unfavorable equilibrium (Keq ~ 10-7 M) in the direction of APS formation, and it has been postulated that the reaction is driven by the hydrolysis of PPi by a ubiquitous inorganic pyrophosphatase [Segel87]. In Escherichia coli K-12 it was found that the enzymes couples the formation of APS to hydrolysis of GTP [Liu94d].

Following sulfate activation, the pathway consists of phosphorylation of APS to PAPS, which is catalyzed by adenylylsulfate kinase (APS kinase), reduction to sulfite, which is catalyzed by the thioredoxin (or glutaredoxin)-dependent 3'-phospho-adenylylsulfate reductase (PAPS reductase), and a final reduction of sulfite to sulfide, catalyzed by a assimilatory sulfite reductase (NADPH).

Superpathways: superpathway of L-methionine biosynthesis (by sulfhydrylation), superpathway of sulfate assimilation and cysteine biosynthesis, superpathway of sulfur amino acid biosynthesis (Saccharomyces cerevisiae)

Subpathways: sulfate activation for sulfonation

Variants: sulfate reduction II (assimilatory), sulfate reduction III (assimilatory), sulfate reduction IV (dissimilatory), sulfate reduction V (dissimilatory)

Unification Links: EcoCyc:SO4ASSIM-PWY

Created 31-Mar-1994 by Riley M, Marine Biological Laboratory
Revised 19-Sep-2006 by Caspi R, SRI International


Berndt04: Berndt C, Lillig CH, Wollenberg M, Bill E, Mansilla MC, de Mendoza D, Seidler A, Schwenn JD (2004). "Characterization and reconstitution of a 4Fe-4S adenylyl sulfate/phosphoadenylyl sulfate reductase from Bacillus subtilis." J Biol Chem 279(9);7850-5. PMID: 14627706

Kredich96: Kredich, N.M. (1996). "Biosynthesis of cysteine." In Escherichia coli and Salmonella typhimurium.Cellular and Molecular Biology (Ed by Neidhard FC) pp. 514-527, American Society for Microbiology, Washington D.C.

Liu94d: Liu C, Martin E, Leyh TS (1994). "GTPase activation of ATP sulfurylase: the mechanism." Biochemistry 33(8);2042-7. PMID: 8117661

Segel87: Segel IH, Renosto F, Seubert PA (1987). "Sulfate-activating enzymes." Methods Enzymol 143;334-49. PMID: 2821345

Thauer77: Thauer RK, Jungermann K, Decker K (1977). "Energy conservation in chemotrophic anaerobic bacteria." Bacteriol Rev 1977;41(1);100-80. PMID: 860983

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Abola99: Abola AP, Willits MG, Wang RC, Long SR (1999). "Reduction of adenosine-5'-phosphosulfate instead of 3'-phosphoadenosine-5'-phosphosulfate in cysteine biosynthesis by Rhizobium meliloti and other members of the family Rhizobiaceae." J Bacteriol 181(17);5280-7. PMID: 10464198

Bairoch93: Bairoch A, Boeckmann B (1993). "The SWISS-PROT protein sequence data bank, recent developments." Nucleic Acids Res. 21:3093-3096. PMID: 8332529

Bairoch93a: Bairoch A, Boeckmann B (1993). "The SWISS-PROT protein sequence data bank, recent developments." Nucleic Acids Res. 21:3093-3096. PMID: 8332529

Berendt95: Berendt U, Haverkamp T, Prior A, Schwenn JD (1995). "Reaction mechanism of thioredoxin: 3'-phospho-adenylylsulfate reductase investigated by site-directed mutagenesis." Eur J Biochem 1995;233(1);347-56. PMID: 7588765

BRENDA14: BRENDA team (2014). Imported from BRENDA version existing on Aug 2014.

Butland05: Butland G, Peregrin-Alvarez JM, Li J, Yang W, Yang X, Canadien V, Starostine A, Richards D, Beattie B, Krogan N, Davey M, Parkinson J, Greenblatt J, Emili A (2005). "Interaction network containing conserved and essential protein complexes in Escherichia coli." Nature 433(7025);531-7. PMID: 15690043

Chartron07: Chartron J, Shiau C, Stout CD, Carroll KS (2007). "3'-Phosphoadenosine-5'-phosphosulfate reductase in complex with thioredoxin: a structural snapshot in the catalytic cycle." Biochemistry 46(13);3942-51. PMID: 17352498

Christner81: Christner JA, Munck E, Janick PA, Siegel LM (1981). "Mossbauer spectroscopic studies of Escherichia coli sulfite reductase. Evidence for coupling between the siroheme and Fe4S4 cluster prosthetic groups." J Biol Chem 1981;256(5);2098-101. PMID: 6257697

Christner83: Christner JA, Munck E, Janick PA, Siegel LM (1983). "Mossbauer evidence for exchange-coupled siroheme and [4Fe-4S] prosthetic groups in Escherichia coli sulfite reductase. Studies of the reduced states and of a nitrite turnover complex." J Biol Chem 258(18);11147-56. PMID: 6309833

Coves93: Coves J, Niviere V, Eschenbrenner M, Fontecave M (1993). "NADPH-sulfite reductase from Escherichia coli. A flavin reductase participating in the generation of the free radical of ribonucleotide reductase." J Biol Chem 1993;268(25);18604-9. PMID: 8360156

Coves93a: Coves J, Eschenbrenner M, Fontecave M (1993). "Sulfite reductase of Escherichia coli is a ferrisiderophore reductase." Biochem Biophys Res Commun 192(3);1403-8. PMID: 8389549

Coves97: Coves J, Zeghouf M, Macherel D, Guigliarelli B, Asso M, Fontecave M (1997). "Flavin mononucleotide-binding domain of the flavoprotein component of the sulfite reductase from Escherichia coli." Biochemistry 1997;36(19);5921-8. PMID: 9153434

Crane95: Crane BR, Siegel LM, Getzoff ED (1995). "Sulfite reductase structure at 1.6 A: evolution and catalysis for reduction of inorganic anions." Science 270(5233);59-67. PMID: 7569952

Dahl90: Dahl, C., Koch, H., Keuken, O., Trueper, H.G. (1990). "Purification and characterization of ATP sulfurylase from the extremely thermophilic archaebacterial sulfate-reducer, Archaeoglobus fulgidus." FEMS Microbiol. Let. 67: 27-32.

DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114

Dyson90: Dyson HJ, Gippert GP, Case DA, Holmgren A, Wright PE (1990). "Three-dimensional solution structure of the reduced form of Escherichia coli thioredoxin determined by nuclear magnetic resonance spectroscopy." Biochemistry 1990;29(17);4129-36. PMID: 2193685

Eklund84: Eklund H, Cambillau C, Sjoberg BM, Holmgren A, Jornvall H, Hoog JO, Branden CI (1984). "Conformational and functional similarities between glutaredoxin and thioredoxins." EMBO J 1984;3(7);1443-9. PMID: 6378624

Eschenbrenner95: Eschenbrenner M, Coves J, Fontecave M (1995). "The flavin reductase activity of the flavoprotein component of sulfite reductase from Escherichia coli. A new model for the protein structure." J Biol Chem 1995;270(35);20550-5. PMID: 7657631

Eschenbrenner95a: Eschenbrenner M, Coves J, Fontecave M (1995). "NADPH-sulfite reductase flavoprotein from Escherichia coli: contribution to the flavin content and subunit interaction." FEBS Lett 1995;374(1);82-4. PMID: 7589518

Evrard99: Evrard A, Zeghouf M, Fontecave M, Roby C, Coves J (1999). "31P nuclear magnetic resonance study of the flavoprotein component of the Escherichia coli sulfite reductase." Eur J Biochem 261(2);430-7. PMID: 10215853

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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