TauD1 (VPARA_23370) is a 302-amino-acid cytosolic Fe(II)/2-oxoglutarate (alpha-ketoglutarate)-dependent taurine dioxygenase (EC 1.14.11.17) in Variovorax paradoxus TBEA6. Belonging to the TauD/TfdA non-heme iron oxygenase family (Pfam PF02668, residues 23-294), TauD1 catalyzes the oxygenolytic desulfonation of taurine (2-aminoethanesulfonate) in the presence of O2 and 2-oxoglutarate to yield sulfite, aminoacetaldehyde, succinate, and CO2. In the rhizosphere, where inorganic sulfate is frequently immobilized in organosulfur esters and sulfonates, TauD1 complements the FMNH2-dependent alkanesulfonate monooxygenase SsuD (VPARA_19220) to liberate assimilable sulfite for bacterial and plant sulfur nutrition.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000908 taurine dioxygenase activity | IEA GO_REF:0000003 | ACCEPT | Summary: Core catalytic activity (EC 1.14.11.17) of TauD1, catalyzing the 2-oxoglutarate-dependent oxygenolytic cleavage of taurine to sulfite and aminoacetaldehyde. Reason: TauD1 (VPARA_23370, 302 aa) spans the full-length TauD/TfdA dioxygenase domain (Pfam PF02668, residues 23-294; PANTHER PTHR30468:SF1) and carries EC 1.14.11.17, matching characterized bacterial alpha-ketoglutarate-dependent taurine dioxygenases. Supporting Evidence: UniProtKB:A0A0H2MHV8 FT DOMAIN 23..294 FT /note="TauD/TfdA-like" FT /evidence="ECO:0000259|Pfam:PF02668" PMID:9287300 The pure enzyme converted taurine to sulfite and aminoacetaldehyde, which was identified by high pressure liquid chromatography after enzymatic conversion to ethanolamine. The reaction also consumed equimolar amounts of oxygen and alpha-ketoglutarate; ferrous iron was absolutely required for activity; and ascorbate stimulated the reaction. |
| GO:0005737 cytoplasm | IEA GO_REF:0000118 | MODIFY | Summary: Correct but broad subcellular localization; refine to GO:0005829 (cytosol) for this soluble cytoplasmic enzyme lacking signal peptides or transmembrane helices. Reason: TauD1 (302 aa) is a soluble intracellular dioxygenase lacking any signal peptide or transmembrane domain, so the more specific descendant term GO:0005829 (cytosol) is appropriate. Proposed replacements: cytosol Supporting Evidence: PMID:9287300 TauD was overexpressed in E. coli to approximately 70% of the total soluble protein and purified to apparent homogeneity by a simple two-step procedure. |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: True broad ancestor term subsumed by the accepted specific catalytic activity GO:0000908 (taurine dioxygenase activity). Reason: GO:0000908 (taurine dioxygenase activity) is a specific descendant of GO:0016491 (oxidoreductase activity) and is already accepted as the core molecular function of TauD1. Supporting Evidence: PMID:9287300 The pure enzyme converted taurine to sulfite and aminoacetaldehyde, which was identified by high pressure liquid chromatography after enzymatic conversion to ethanolamine. The reaction also consumed equimolar amounts of oxygen and alpha-ketoglutarate; ferrous iron was absolutely required for activity; and ascorbate stimulated the reaction. |
| GO:0016706 2-oxoglutarate-dependent dioxygenase activity | IEA GO_REF:0000118 | TOO GENERAL | Summary: True direct parent term subsumed by the accepted specific catalytic activity GO:0000908 (taurine dioxygenase activity). Reason: GO:0000908 (taurine dioxygenase activity) is a direct is_a child of GO:0016706 (2-oxoglutarate-dependent dioxygenase activity) and is already accepted as the core molecular function of TauD1. Supporting Evidence: PMID:9287300 The pure enzyme converted taurine to sulfite and aminoacetaldehyde, which was identified by high pressure liquid chromatography after enzymatic conversion to ethanolamine. The reaction also consumed equimolar amounts of oxygen and alpha-ketoglutarate; ferrous iron was absolutely required for activity; and ascorbate stimulated the reaction. |
| GO:0005506 iron ion binding | IC PMID:9287300 Characterization of alpha-ketoglutarate-dependent taurine di... | NEW | Summary: Core catalytic cofactor binding; TauD family dioxygenases require a mononuclear non-heme Fe(II) center coordinated by a conserved 2-His-1-carboxylate facial triad. Reason: TauD1 spans the full-length TauD/TfdA-like dioxygenase domain (Pfam PF02668, residues 23-294) and conserves the mononuclear non-heme Fe(II)-binding 2-His-1-carboxylate facial triad (His118, Asp120, His278 in VPARA_23370, corresponding to His99, Asp101, His255 in E. coli TauD) essential for O2 activation. Supporting Evidence: UniProtKB:A0A0H2MHV8 FT DOMAIN 23..294 FT /note="TauD/TfdA-like" FT /evidence="ECO:0000259|Pfam:PF02668" PMID:9287300 The reaction also consumed equimolar amounts of oxygen and alpha-ketoglutarate; ferrous iron was absolutely required for activity; and ascorbate stimulated the reaction. |
| GO:0019529 taurine catabolic process | IC PMID:9287300 Characterization of alpha-ketoglutarate-dependent taurine di... | NEW | Summary: Core biological process of TauD1, which degrades taurine to sulfite and aminoacetaldehyde for sulfur assimilation under sulfate limitation. Reason: Existing GOA annotations for VPARA_23370 lack any biological process term; TauD1 (EC 1.14.11.17) catalyzes the committed oxygenolytic desulfonation step of taurine catabolism (GO:0019529). Supporting Evidence: PMID:9287300 The Escherichia coli tauD gene is required for the utilization of taurine (2-aminoethanesulfonic acid) as a sulfur source and is expressed only under conditions of sulfate starvation. UniProtKB:A0A0H2MHV8 FT DOMAIN 23..294 FT /note="TauD/TfdA-like" FT /evidence="ECO:0000259|Pfam:PF02668" |
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Download this section (compressed HTML)Q: How are tauD1 (VPARA_23370) and the ssuEADCB alkanesulfonate monooxygenase system (ssuD / VPARA_19220) differentially regulated in Variovorax paradoxus TBEA6 during growth on taurine, aliphatic sulfonates, and plant root exudates under sulfate starvation?
Suggested experts: Kertesz MA, Steinbuechel A, Hausinger RP
Experiment: Purify recombinant His-tagged V. paradoxus TauD1 (VPARA_23370) and measure steady-state Fe(II)/2-oxoglutarate-dependent sulfite release across taurine, isethionate, MOPS, and pentanesulfonate, alongside growth phenotyping of single ΞtauD1, ΞssuD, and double ΞtauD1 ΞssuD mutants on organosulfonates as sole sulfur source.
Hypothesis: TauD1 exhibits highest catalytic efficiency toward taurine whereas SsuD processes broader aliphatic sulfonates, and together they provide dual oxygenolytic desulfonation routes in the rhizosphere.
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