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Literature summary for 4.2.1.112 extracted from

  • Boll, M.; Einsle, O.; Ermler, U.; Kroneck, P.M.H.; Ullmann, G.M.
    Structure and function of the unusual tungsten enzymes acetylene hydratase and class II benzoyl-coenzyme A reductase (2016), J. Mol. Microbiol. Biotechnol., 26, 119-137 .
    View publication on PubMed

Crystallization (Commentary)

Crystallization (Comment) Organism
high resolution crystal structure determination of the W-dependent enzyme crystallized under the exclusion of dioxygen (N2/H2 (94%/6% v/v)) at 1.26 A resolution, PDB ID 2E7Z Syntrophotalea acetylenica

Protein Variants

Protein Variants Comment Organism
C141S site-directed mutagenesis Syntrophotalea acetylenica
D13A site-directed mutagenesis of catalytically important Asp13, a direct neighbor of the [4Fe-4S] coordinating Cys12, forms a close hydrogen bond of 2.41 A to the oxygen ligand of the W ion, the mutant shows significant loss of activity compared to wild-type Syntrophotalea acetylenica
D13E site-directed mutagenesis of catalytically important Asp13, a direct neighbor of the [4Fe-4S] coordinating Cys12, forms a close hydrogen bond of 2.41 A to the oxygen ligand of the W ion, the mutant shows unaltered activity compared to wild-type Syntrophotalea acetylenica
I142A site-directed mutagenesis, Ile142 is part of the hydrophobic ring that is proposed to form the substrate binding cavity at the end of the access tunnel towards the active site, its exchange against alanine results in a strong loss of activity Syntrophotalea acetylenica
K48A site-directed mutagenesis of the residue involved in electron transfer between the two cofactors, the exchange of Lys48 against alanine does not affect catalysis Syntrophotalea acetylenica

Inhibitors

Inhibitors Comment Organism Structure
cyanide a cyanide sensitive enzyme Syntrophotalea acetylenica
additional information oxidation of AH with one equivalent [Fe(CN)6]3- Syntrophotalea acetylenica

Localization

Localization Comment Organism GeneOntology No. Textmining
soluble the enzyme activity is localized exclusively in the soluble fraction of the cell extract Syntrophotalea acetylenica
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Metals/Ions

Metals/Ions Comment Organism Structure
Fe2+ in [4Fe-4S] cluster, the enzyme contains 3.7-3.9 mol Fe/mol enzyme Syntrophotalea acetylenica
Molybdenum a Mo-dependent active form of AH (Mo-AH) can also be obtained from Pelobacter acetylenicus Syntrophotalea acetylenica
additional information the dependence of AH activity on the applied redox potential gives a midpoint potential of -340 mV. Mo-dependent enzyme is approximately 10fold less active than the native W-dependent enzyme. W is generally preferred over Mo in low-potential redox catalysis Syntrophotalea acetylenica
Tungsten bound with two pyranopterins, the enzyme contains 0.4-0.5 mol W/mol enzyme Syntrophotalea acetylenica

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
acetylene + H2O Syntrophotalea acetylenica
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acetaldehyde
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r

Organism

Organism UniProt Comment Textmining
Syntrophotalea acetylenica Q71EW5
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Reaction

Reaction Comment Organism Reaction ID
acetaldehyde = acetylene + H2O acetylene hydratase harbors two pyranopterins bound to tungsten, and a [4Fe-4S] cluster. Tungsten is coordinated by four dithiolene sulfur atoms, one cysteine sulfur, and one oxygen ligand. The enzyme activity requires a strong reductant suggesting (IV) as the active oxidation state. Two different types of reaction pathways have been proposed, the reaction does not involve a net electron transfer. The nature of the oxygen ligand of the W center in the enzyme is crucial to formulate a reaction mechanism. Residue Asp13 is catalytically important because it activates the oxygen atom for the addition to the C-C triple bond. Reaction mechanism analysis, overview Syntrophotalea acetylenica

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
acetylene + H2O
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Syntrophotalea acetylenica acetaldehyde
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additional information the enzyme is highly specific for acetylene Syntrophotalea acetylenica ?
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Subunits

Subunits Comment Organism
? x * 83500, about, mass spectrometry Syntrophotalea acetylenica
More domain I (residues 4-60) harbors the [4Fe-4S] cluster, ligated by the four cysteine residues Cys9, Cys12, Cys16 and Cys46. Domains II (residues 65-136 and 393-542) and III (residues 137-327) have an alphabetaalpha-fold with homologies to the NAD-binding fold of dehydrogenases Syntrophotalea acetylenica

Cofactor

Cofactor Comment Organism Structure
additional information cofactors bis-WPT guanine dinucleotide and [4Fe-4S] cluster are buried deep inside a four-domain fold, as typically observed for enzymes of the DMSOR family Syntrophotalea acetylenica
tungsto-bis(pyranopterin guanine dinucleotide) the enzyme harbors two pyranopterins bound to tungsten, structure overview Syntrophotalea acetylenica
[4Fe-4S] cluster low potential ferredoxin-type [4Fe-4S] cluster, the [4Fe-4S] has a midpoint potential around -410 mV Syntrophotalea acetylenica

General Information

General Information Comment Organism
evolution the enzyme belongs to the tungsten containing enzymes, and is a member of the dimethyl sulfoxide reductase (DMSOR) family of enzymes. The W center coordinated by the two MGDs with the [4Fe-4S] cluster in close proximity, is unique for an enzyme of the DMSOR family Syntrophotalea acetylenica
additional information Mo-dependent enzyme is approximately 10fold less active than the native W-dependent enzyme. Active site cavity structure of Pelobacter acetylenicus acetylene hydratase, overview. A C2H2 molecule docked computationally at the AH active site gives an excellent fit in the pocket of the hydrophobic ring with its carbon atoms positioned directly above the oxygen ligand and the carboxylic acid group of active site residue Asp13 Syntrophotalea acetylenica