Characterization of α-Ketoglutarate-dependent Taurine Dioxygenase from Escherichia coli
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. The sequence relatedness of the TauD protein to the α-ketoglutarate-dependent 2,4-dichlorophenoxyacetate dioxygenase...
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Veröffentlicht in: | The Journal of biological chemistry 1997-09, Vol.272 (37), p.23031-23036 |
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Zusammenfassung: | 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. The sequence relatedness of the TauD protein to the α-ketoglutarate-dependent 2,4-dichlorophenoxyacetate dioxygenase of Alcaligenes eutrophus suggested that TauD is an α-ketoglutarate-dependent dioxygenase catalyzing the oxygenolytic release of sulfite from taurine (van der Ploeg, J. R., Weiss, M. A., Saller, E., Nashimoto, H., Saito, N., Kertesz, M. A., and Leisinger, T. (1996) J. Bacteriol. 178, 5438–5446). TauD was overexpressed in E. coli to ∼70% of the total soluble protein and purified to apparent homogeneity by a simple two-step procedure. The apparent Mr of 81,000 of the native protein and the subunit Mrof 37,400 were consistent with a homodimeric structure. 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 α-ketoglutarate; ferrous iron was absolutely required for activity; and ascorbate stimulated the reaction. The properties and amino acid sequence of this enzyme thus define it as a new member of the α-ketoglutarate-dependent dioxygenase family. The pure enzyme showed maximal activity at pH 6.9 and retained activity on storage at −20 °C for several weeks. Taurine (Km = 55 μm) was the preferred substrate, but pentanesulfonic acid, 3-(N-morpholino)propanesulfonic acid, and 1,3-dioxo-2-isoindolineethanesulfonic acid were also desulfonated at significant rates. Among the cosubstrates tested, only α-ketoglutarate (Km = 11 μm) supported significant dioxygenase activity. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.272.37.23031 |