Perchlorate reductase 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 ...

that catalyzes 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 ...

s: :ClO₄⁻ + 2 AH₂

\rightleftharpoons

ClO₂⁻ + 2 A + 2 H₂O and :ClO₃⁻ + AH₂

\rightleftharpoons

ClO₂⁻ + A + H₂O Thus, the substrates of this enzyme are a reduced electron acceptor (denoted AH₂) and either chlorate or

perchlorate A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. Per ...

, sometimes collectively denoted as (per)chlorate. The

product Product may refer to: Business * Product (business), an item that serves as a solution to a specific consumer problem. * Product (project management), a deliverable or set of deliverables that contribute to a business solution Mathematics * Produ ...

s are chlorite, an oxidized electron acceptor (denoted A), and

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

. It is closely related to the enzyme chlorate reductase, but is distinguished by its ability to reduce both perchlorate and chlorate, whereas chlorate reductase only acts on chlorate. Perchlorate reductase and chlorate reductase are closely related but form genetically distinct clades. As of February 2023, perchlorate reductase has not been assigned a specific

Enzyme Commission number The Enzyme Commission number (EC number) is a numbering scheme, numerical classification scheme for enzymes, based on the chemical reactions they catalysis, catalyze. As a system of enzyme nomenclature, every EC number is associated with a recomme ...

, but along with chlorate reductase (), it would presumably be a member of the EC 1.97.1.-

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 u ...

subclass. Some databases, including

BRENDA Brenda is a feminine given name in the English language. Origin The overall accepted origin for the female name Brenda is the Old Nordic male name ''Brandr'' meaning both ''torch'' and ''sword'': evidently the male name Brandr took root in areas ...

, currently combine perchlorate reductase and chlorate reductase listings.

Structure

Perchlorate reductase is usually encoded as a combination of four genes, denoted pcrABCD. The active subunits are pcrA and pcrB which form a

periplasm The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found that ...

ic dimer similar to the active complex in nitrate reductase. pcrC is a believed to be 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 bi ...

that connects the AB complex to the membrane and allows for electron shuttling. The function of pcrD is uncertain, but may encode a molybdenum-containing chaperone protein specific to assembling the pcrABC system. All known functional perchlorate reductase enzymes include genetically similar versions of pcrABCD except for the

Campylobacterota Campylobacterota are a phylum of bacteria. All species of this phylum are Gram-negative. The Campylobacterota consist of few known genera, mainly the curved to spirilloid ''Wolinella'' spp., ''Helicobacter'' spp., and ''Campylobacter'' spp. Most ...

'' Arcobacter'' strain CAB, which lacks a traditional pcrC and appears to have replaced it with an unrelated Campylobacterota cytochrome. All characterized organisms that encode perchlorate reductase also have the enzyme

chlorite dismutase Chlorite dismutase, also known as Chlorite O2-lyase (), is an enzyme that catalyzes the chemical reaction : ClO → Cl− + O2 Reactions that generate oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It ...

, which reduces the chlorite produced by perchlorate reductase, and prevents this reactive compound from accumulating to toxic levels. The pcrABCD and chlorite dismutase gene are typically located together in the bacterial genome.

References

Literature

* * {{Portal bar, Biology, border=no, Chemistry EC 1.97.1 Enzymes of known structure