Exonuclease
Exonuclease
Exonuclease (/ɛkˈsoʊnjuːkleɪs/) is an enzyme that cleaves nucleotides one at a time from the end (exo) of a polynucleotide chain. This process is known as exonucleolytic cleavage, which is essential for many DNA repair mechanisms.
Etymology
The term "exonuclease" is derived from the Greek words "exo" meaning "outside" and "nuclease" which is a portmanteau of "nucleic acid" and "hydrolase".
Function
Exonucleases are involved in the processes of DNA replication, DNA repair, and recombination. They play a crucial role in maintaining the integrity of genetic information by removing mismatched bases, damaged nucleotides, or inappropriate bases inserted during replication.
Types
There are two main types of exonucleases: 3' to 5' exonucleases and 5' to 3' exonucleases. The numbers refer to the direction in which the exonuclease works on the DNA strand.
- 3' to 5' exonucleases remove nucleotides from the 3' end of the DNA molecule. This type of exonuclease is often associated with the DNA polymerase enzyme, which synthesizes new DNA strands.
- 5' to 3' exonucleases remove nucleotides from the 5' end of the DNA molecule. This type of exonuclease is often involved in DNA repair mechanisms, such as the removal of damaged nucleotides.
Related Terms
- Endonuclease: An enzyme that cleaves nucleotides from within a polynucleotide chain, as opposed to from the ends.
- Nuclease: A general term for enzymes that cleave nucleic acids.
- DNA repair: The collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome.
- DNA replication: The process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules.
External links
- Medical encyclopedia article on Exonuclease
- Wikipedia's article - Exonuclease
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