enzymology 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 ...

, a phosphoadenylyl-sulfate reductase (thioredoxin) () is an enzyme 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 :adenosine 3',5'-bisphosphate + sulfite + thioredoxin disulfide

\rightleftharpoons

3'-phosphoadenylyl sulfate + thioredoxin The 3 substrates of this enzyme are

adenosine 3',5'-bisphosphate Adenosine 3',5'-bisphosphate is a form of an adenosine nucleotide with two phosphate groups attached to different carbons in the ribose ring. This is distinct from adenosine diphosphate, where the two phosphate groups are attached in a chain to th ...

sulfite Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid ( sulfurous acid) is elusive, its salts are wide ...

, and

thioredoxin disulfide Thioredoxin is a class of small redox proteins known to be present in all organisms. It plays a role in many important biological processes, including redox signaling. In humans, thioredoxins are encoded by ''TXN'' and '' TXN2'' genes. Loss-o ...

, whereas its two products are 3'-phosphoadenylyl sulfate and thioredoxin. This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with a disulfide as acceptor. The systematic name of this enzyme class is adenosine 3',5'-bisphosphate,sulfite:thioredoxin-disulfide oxidoreductase (3'-phosphoadenosine-5'-phosphosulfate-forming). Other names in common use include PAPS reductase, thioredoxin-dependent, PAPS reductase, thioredoxin:adenosine 3'-phosphate 5'-phosphosulfate reductase, 3'-phosphoadenylylsulfate reductase, thioredoxin:3'-phospho-adenylylsulfate reductase, phosphoadenosine-phosphosulfate reductase, adenosine 3',5'-bisphosphate,sulfite:oxidized-thioredoxin, and oxidoreductase (3'-phosphoadenosine-5'-phosphosulfate-forming). This enzyme participates in sulfur metabolism.

Structural studies

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and .

References

* EC 1.8.4 Enzymes of known structure {{1.8-enzyme-stub