Enzyme

1.14.11.17 - Taurine dioxygenase

Alternative Name(s)
  • Alpha-ketoglutarate-dependent taurine dioxygenase.
  • 2-aminoethanesulfonate dioxygenase.

Catalytic Activity

2-oxoglutarate + O2 + taurine = aminoacetaldehyde + CO2 + H(+) + succinate + sulfite

Cofactors

Fe(2+); L-ascorbate.

Reaction Mechanism

    taurine dioxygenase By Reference

    Taurine:alpha-ketoglutarate dioxygenase (TauD) hydroxylates C1 of taurine (2-aminoethane-1-sulfonic acid) and other organosulfates, leading to elimination of sulfite and thereby initiating the acquisition of sulphur from compounds that contain the element in a form that would otherwise be biologically inert. Escherichia coli expresses TauD only in the absence of sulfate. The reaction requires molecular dioxygen and 2-oxoglutarate as a cosubstrate.

    In the resting state, Fe(II) is coordinated by His99, Asp 101, His 255 and three water molecules. The cosubstrate 2-oxoglutarate binds to Fe(II) via the carbonyls on C1 and C2, displacing two water molecules. Taurine binds (not to Fe(II)), displacing the third water molecule. Dioxygen binds to Fe(II) via one of the oxygen atoms; this formally oxidises iron to Fe(III). The radical on the O-O bond attacks C2 of 2-oxoglutarate, with the C2 carbonyl attacking and oxidising iron to Fe(IV). The cosubstrate is decarboxylated with C1 leaving as carbon dioxide. This is concomitant with heterolytic O-O bond cleavage and oxidation of the cosubstrate, giving an Fe(IV)=O oxoferryl intermediate with bound succinate. The oxo atom abstracts the taurine C1 hydrogen in a radical mechanism, with reduction of iron to Fe(III)-OH, leaving a radical on taurine. The taurine radical is hydroxylated with OH to give 1-hydroxytaurine, with reduction of iron to Fe(II), regenerating the initial oxidation state. 1-hydroxytaurine decomposes to give sulfite and aminoacetaldehyde. Arg 270 changes its hydrogen bonding to the cosubstrate during the reaction, and may initiate the decarboxylation step or help to remove carbon dioxide from the metal coordination sphere.
    Catalytic Residues
    AA Uniprot Uniprot Resid PDB PDB Resid
    Arg P37610 270 1os7 270
    His P37610 99 1os7 99
    Asp P37610 101 1os7 101
    His P37610 255 1os7 255
    Step Components

    cofactor used, radical termination, reaction occurs outside the enzyme, overall reactant used, overall product formed, native state of cofactor regenerated, electron transfer, decarboxylation, hydrogen transfer, decoordination from a metal ion, radical formation, bimolecular homolytic substitution, native state of enzyme regenerated, intermediate collapse, intermediate formation, coordination to a metal ion, bimolecular homolytic addition, intermediate terminated, bimolecular nucleophilic addition, redox reaction, unimolecular elimination by the conjugate base

    Step 1.

    Fe(II) donates a single electron to the dioxygen molecule, resulting in the dioxygen being bound to the Fe(III) centre.

    Step 2.

    Fe(III) donates a single electron to the bound peroxo group. The terminal oxygen of the peroxo group attacks the carbonyl carbon of the 2-oxoglutarate substrate in a nucleophilic addition.

    Step 3.

    Carbon dioxide is eliminated from the intermediate to form succinate and a iron-bound oxo anion.

    Step 4.

    The iron-bound oxo anion donates an electron to the Fe(IV) centre and abstracts a proton from the taurine substrate.

    Step 5.

    The carbon radical initiates a homolytic subsitution which forms the 1-hydroxy-2-aminoethanesulfonic acid product and results in a single electron transfer to the Fe(III) centre.

    Step 6.

    The 1-hydroxy-2-aminoethanesulfonic acid decomposes to aminoacetaldehyde and sulfite.

    Products.

    The products of the reaction.

Reaction Parameters

  • Kinetic Parameters
    Organism KM Value [mM] Substrate Comment
    Escherichia coli 0.00000001 O2 substrate 2-methyltaurine
    Bacteria 1.01 O2
  • Temperature

    There are no reaction parameters information for this Enzyme.

  • pH

    There are no reaction parameters information for this Enzyme.

Associated Proteins

Protein name Organism
Alpha-ketoglutarate-dependent taurine dioxygenase Escherichia coli (strain K12)
Alpha-ketoglutarate-dependent taurine dioxygenase oxidoreductase protein Herbaspirillum seropedicae (strain SmR1)
Shy7-dioxygenase Streptomyces fulvissimus DSM 40593
Dioxygenase, TauD/TfdA Burkholderia pseudomallei
Putative taurine dioxygenase,2-oxoglutarate-dependent Rhizobium mesoamericanum STM3625

Citations