# Exoribonuclease

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> Source: https://en.wikipedia.org/wiki/Exoribonuclease
> Source revision: 1343611633
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{{Short description|Class of enzymes that degrade RNA}}
{{No footnotes|date=March 2026}}
thumb|Reaction diagrams for both hydrolytic (left) and phosphorolytic (right) 3'-5' exoribonuclease degradation of RNA.

An '''exoribonuclease''' is an [exonuclease](/source/exonuclease) [ribonuclease](/source/ribonuclease), which are enzymes that degrade [RNA](/source/RNA) by removing terminal [nucleotide](/source/nucleotide)s from either the [5' end](/source/5'_end) or the [3' end](/source/3'_end) of the RNA molecule. Enzymes that remove nucleotides from the 5' end are called ''5'-3' exoribonucleases'', and enzymes that remove nucleotides from the 3' end are called ''3'-5' exoribonucleases''.

Exoribonucleases can use either water to cleave the nucleotide-nucleotide bond (which is called hydrolytic activity) or [inorganic phosphate](/source/inorganic_phosphate) (which is called phosphorolytic activity). Hydrolytic exoribonucleases are classified under [EC number](/source/Enzyme_Commission_number) 3.1 and phosphorolytic exoribonucleases under EC number 2.7.7. As the phosphorolytic enzymes use inorganic phosphate to cleave bonds they release [nucleotide diphosphates](/source/Adenosine_diphosphate), whereas the hydrolytic enzymes (which use water) release [nucleotide monosphosphates](/source/Adenosine_monophosphate).

Exoribonucleases exist in all kingdoms of life, the [bacteria](/source/bacteria), [archaea](/source/archaea), and [eukaryote](/source/eukaryote)s. Exoribonucleases are involved in the degradation of many different RNA species, including [messenger RNA](/source/messenger_RNA), [transfer RNA](/source/transfer_RNA), [ribosomal RNA](/source/ribosomal_RNA) and [miRNA](/source/miRNA). Exoribonucleases can be single proteins (such as [RNase D](/source/RNase_D) or [RNase PH](/source/RNase_PH)) but also can be complexes of multiple proteins, such as the [exosome complex](/source/exosome_complex) (in which four of the major exoribonuclease families are represented).

==Major families==
{| class="wikitable"
!Family
!Example members
!Distribution
!Catalytic activity
|-
|rowspan="3"| RNR || [RNase R](/source/RNase_R)
|rowspan="3"| Most bacteria, all eukaryotes
|rowspan="3"| 3'-5' hydrolytic
|-
|[RNase II](/source/Ribonuclease_T2)
|-
|[Rrp44](/source/Exosome_complex)
|-
|rowspan="4"| DEDD || [RNase D](/source/RNase_D)
|rowspan="4"| Certain bacteria, all eukaryotes
|rowspan="4"| 3'-5' hydrolytic
|-
|[RNase T](/source/RNase_T)
|-
|[PM/Scl-100](/source/Exosome_complex)
|-
|[Oligoribonuclease](/source/Oligoribonuclease)
|-
|rowspan="1"| RBN || [RNase BN](/source/RNase_BN)
|rowspan="1"| Certain bacteria
|rowspan="1"| 3'-5' hydrolytic
|-
|rowspan="3"| PDX || [PNPase](/source/Polynucleotide_Phosphorylase)
|rowspan="3"| All kingdoms
|rowspan="3"| 3'-5' phosphorolytic
|-
|[PM/Scl-75](/source/Exosome_complex)
|-
|[RNase PH](/source/RNase_PH)
|-
|rowspan="1"| RRP4 || [Rrp4](/source/Exosome_complex)
|rowspan="1"| All eukaryotes, most archaea
|rowspan="1"| 3'-5' hydrolytic
|-
|rowspan="2"| 5PX || [Exoribonuclease I](/source/Exoribonuclease_I)
|rowspan="2"| All eukaryotes
|rowspan="2"| 5'-3' hydrolytic
|-
|[Exoribonuclease II](/source/Exoribonuclease_II)
|}

== See also ==
* [Endoribonuclease](/source/Endoribonuclease)
* [Nuclease](/source/Nuclease)
* [Deoxyribonuclease](/source/Deoxyribonuclease)
* [Exodeoxyribonuclease](/source/Exodeoxyribonuclease)
* [Endodeoxyribonuclease](/source/Endodeoxyribonuclease)

== References ==
*{{cite journal
|author1=Zuo Y |author2=Deutscher MP. |title=Exoribonuclease superfamilies: structural analysis and phylogenetic distribution
|journal=Nucleic Acids Res.
|volume=29
|pages=1017–26
|year=2001
|pmid=11222749
|doi=10.1093/nar/29.5.1017
|issue=5
|pmc=56904
}}

==External links==
* {{MeshName|Exoribonucleases}}

{{Nucleases}}
{{Kinases}}

Category:EC 3.1
Category:Ribonucleases

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Adapted from the Wikipedia article [Exoribonuclease](https://en.wikipedia.org/wiki/Exoribonuclease) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Exoribonuclease?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.