Taurine dioxygenase

Eichhorn E, JR van der Ploeg, MA Kertesz, T Leisinger (1997) Characterization of an a-ketoglutarate-depen-dent taurine dioxygenase from Escherichia coli. J Biol Chem 272 23031-23036. 

Fig. 2. Active site of taurine dioxygenase (TauD) with 2-oxoglutarate bound to Fe(II) and a taurine substrate (PDB-Code 1GY9) (31).

Fig. 7. (a) Active site of Taurine dioxygenase TauD after activation by the taurine substrate and (b) a benzoylformato model [Fe(bdtbpza)(02CC(0)Ph)] (6). 

Scheme 2.2 Examples of reactions catalyzed by and RNA by the protein AlkB [54] (R = sugar al

Scheme 2.3 Proposed catalytic cycle for taurine dioxygenase as an example of aKG-dependent enzymes [8, 11, 15], The amino acids are numbered according to the sequence of taurine dioxygenase from E. coli [53],...

Only since 2003 has there been spectroscopic evidence to support that monomeric, nonheme iron oxygenases cleave O2 and form Fe(IV)=0 species. These findings came from studies on taurine dioxygenase (TauD), a member of the Fe(If)/a-ketoglutarate (a-KG)-dependent hydroxylase superfamily of enzymes [48]. A generic mechanism proposed for hydroxylation is shown in Fig. 6.19 and includes an Fe(IV)=0 intermediate as the competent H-atom abstractor. 

The archetype Fe(II)/aKG hydroxylase is taurine/ q KG dioxygenase (TauD), an Escherichia coli enzyme that catalyzes the conversion of taurine (2-aminoethanesulfonic acid) to sulfite and aminoacetaldehyde, as illustrated in Scheme 1. TauD catalyzes the hydroxylation of a C H bond on the carbon adjacent to the sulfonate group of taurine. The product of this reaction then decomposes to yield hydrogen sulfite, which serves as an important source of sulfur for many microorganisms. A catalytic mechanism that has been proposed for these enzymes is provided as Scheme 2. Prior to the activation and hydroxylation of the Ci carbon on taurine, q KG binds to the Fe(II) center as a chelate, displacing two of the coordinated waters. Taurine then binds to the enzyme in the vicinity of the Fe(II) center, displacing the remaining water. 

Price JC, Barr EW, Tirupati B, Bollinger JM Jr, Krebs C. The first direct characterization of a high-valent iron intermediate in the reaction of an alpha-ketoglutarate-dependent dioxygenase a high-spin FePV complex in taurine/alpha-ketoglutarate dioxygenase (TauD) from Escherichia coli. Biochemistry 2003 42 7497-7508. 

The resonance Raman spectra of Fe(IV) complexes [(L)FeO]2+, where L = pentadentate pyridylamine ligands, include vFe=0 at 752 cm-1.298 Transient resonance Raman spectra of oxygen intermediates in the non-haem iron enzyme taurine/a-ketoglutarate dioxygenase, include characteristic bands at 812 (160)/787 (lsO) cm-1 and 583 (160)/555 (lsO) cm-1.299 Oxidised intermediates of cytochrome c oxidase give resonance Raman bands for vFe=0 showing that there are three different forms present.300... 

High-valent iron intermediates have been proposed as the active species in OAT and C-H oxidation reactions for nonheme iron enzymes. In some cases, such intermediates have been trapped by rapid fireeze-quench studies and characterized. In ribonucleotide reductase from E. coli and MMO, intermediates X and Q with Fem-( l-0)2-Ferv and Ferv-( 0,-O)2-FeIV diamond core, respectively, have been characterized (Figure 3.11).35 Also, Fe,v oxo intermediates have been observed for mononuclear proteins such as taurine/2-oxoglutarate dioxygenase (TauD) (Figure 3.11).36... 

DPPH = 2,2-diphenyl-l-picrylhydrazyl ENDOR= electron-nuclear double resonance EPR = electron paramagnetic resonance ESE = electron spin echoes ESEEM = electron spin echo envelope modulation FFT = fast fourier transformations FWHM = full width at half maximum HYSCORE = hyperline sublevel correlation nqi = nuclear quadrupole interaction TauD = taurine/aKG dioxygenase TWTA = traveling wave tube amplifier ZFS = zero field splitting. 

Cysteamine is oxidized by cysteamine dioxygenase (EC 1.13.11.19) to hypotaurine, which is then oxidized to taurine by an as yet unidentified enzyme. 

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