Arsenate reductase (azurin) () is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

that

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

the

chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...

:arsenite + H₂O + 2 azurin_ox

\rightleftharpoons

arsenate + 2 azurin_red + 2 H⁺ The 3 substrates of this enzyme are arsenite,

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

, and oxidised

azurin Azurin is a small, periplasmic, bacterial blue copper protein found in ''Pseudomonas'', ''Bordetella'', or ''Alcaligenes'' bacteria. Azurin moderates single-electron transfer between enzymes associated with the cytochrome chain by undergoing oxida ...

, whereas its 3 products are arsenate, reduced

, and

hydrogen ion A hydrogen ion is created when a hydrogen atom loses or gains an electron. A positively charged hydrogen ion (or proton) can readily combine with other particles and therefore is only seen isolated when it is in a gaseous state or a nearly particle ...

Classification

This enzyme belongs to the family of

oxidoreductase In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This group of enzymes usually ut ...

s, specifically those acting on phosphorus or arsenic in donor with a

copper protein Copper proteins are proteins that contain one or more copper ions as prosthetic groups. Copper proteins are found in all forms of air-breathing life. These proteins are usually associated with electron-transfer with or without the involvement o ...

as acceptor.

Nomenclature

The systematic name of this enzyme class is arsenite:azurin oxidoreductase. This enzyme is also called arsenite oxidase.

Structure and function

The enzyme contains a molybdopterin centre comprising two molybdopterin

guanosine dinucleotide Guanosine ( symbol G or Guo) is a purine nucleoside comprising guanine attached to a ribose (ribofuranose) ring via a β-N9-glycosidic bond. Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate ( ...

cofactors bound to

molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...

, a Fe-4Scluster and a Rieske-type Fe-2Scluster. Also uses a c-type

cytochrome Cytochromes are redox-active proteins containing a heme, with a central Fe atom at its core, as a cofactor. They are involved in electron transport chain and redox catalysis. They are classified according to the type of heme and its mode of bin ...

or as acceptors.

References

* * {{Portal bar, Biology, border=no EC 1.20.9 Enzymes of unknown structure