Overview for MACiE Entry M0144
EC Number: 126.96.36.199 (A member of the Oxidoreductases, Acting on phosphorus or arsenic in donors, With other, known, acceptors)
Enzyme Name: arsenite oxidase
Biological Species: Alcaligenes faecalis (Bacteria)
Catalytic Chain UniprotKB Accession Codes:
- Q7SIF4 - Arsenite oxidase large subunit
- Q7SIF3 - Arsenite oxidase small subunit
Representative PDB Code: 1g8k - CRYSTAL STRUCTURE ANALYSIS OF ARSENITE OXIDASE FROM ALCALIGENESFAECALIS (Resolution = 1.64 Å).
Catalytic CATH Codes:
- 188.8.131.52 - Dimethylsulfoxide Reductase, domain 2
- 184.108.40.206 - 'Rieske'-like iron-sulphur domains
- Unassigned Domain
"Other" CATH Codes:
Display structure information
It is unknown whether this reaction is reversible or not.
Overall Comment: The Mo atom is bound to two pterin cofactors (MGD5001 and MGD5002 in the crystal structure) but only one of them is shown in the diagrams for easy of readability. The electron acceptors for this reaction are either azurin or cytochrome c.
The enzyme does not return to a state in which it can catalyse another reaction
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Stepwise Description of the Reaction
|Step 1||Arsenic of the arsenite substrate attacks one of the molybdenum coordinating oxo groups, resulting in a Mo(VI) to Mo(IV) reduction.|
|Step 2||The attacking oxo group forms a second bond to the arsenic, forming the product arsenate and resulting in the loss of the oxo group from the molybdenum complex and the remaining oxo group binding in a much stronger interaction.|
|Step 3||An unidentified base activates water to attack the Mo(IV), forming a hydroxide group in place of the lost oxo group in a nucleophilic addition to the Mo(IV).|
|Step 4||A second unidentified base deprotonates the Mo-bound hydroxide, reforming the oxo group. This results in a single electron transfer through the pterin portion of the cofactor, main chain carbonyl of Ser238, thiolate of Cys24, an iron-sulfur cluster, the peptide bond of Ser99-Ser98, His62B, a second iron-sulfur complex and His81B and finally yields the electron to a bound azurin and resulting in Mo(V).|
|Step 5||The second single electron is transferred from Mo(V) through the pterin portion of the cofactor, main chain carbonyl of Ser238, thiolate of Cys24, an iron-sulfur cluster, the peptide bond of Ser99-Ser98, His62B, a second iron-sulfur complex and His81B and finally yields the electron to a bound azurin. This regenerates the enzyme's Mo(VI) oxidation state.|
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Catalytic Residues Involved
||Location of Function
||Main Chain Carbonyl
||Main Chain Amide
||Main Chain Carbonyl
Organic Cofactors for M0144
|Molybdopterin guanosine dinucleotide
Metal Cofactors for M0144
- P. J. Ellis et al. (2001), Structure, 9, 125-132. Crystal structure of the 100 kDa arsenite oxidase from Alcaligenes faecalis in two crystal forms at 1.64 A and 2.03 A.
- T. Conrads et al. (2002), J. Am. Chem. Soc., 124, 11276-11277. The active site of arsenite oxidase from Alcaligenes faecalis.
- K. R. Hoke et al. (2004), Biochemistry, 43, 1667-1674. Electrochemical studies of arsenite oxidase: an unusual example of a highly cooperative two-electron molybdenum center.
Homologue information for M0144 (1g8k)
MACiE Homologues (within the PDB)
MACiE Homologues (within UniprotKB/SwissProt)
Entries with at least one Catalytic CATH code in common (different mechanisms):
|M0276 ||nitrate reductase |
|M0208 ||ubiquinol-cytochrome-c reductase |
|M0130 ||naphthalene 1,2-dioxygenase |
View a comparison of the other reactions in MACiE with the CATH domain 0.0.0.0
View a comparison of the other reactions in MACiE with the CATH domain 220.127.116.11
Links to this entry in other databases