Exonuclease

Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3’ or the 5’ end occurs. Its close relative is the endonuclease, which cleaves phosphodiester bonds in the middle (endo) of a polynucleotide chain. Eukaryotes and prokaryotes have three types of exonucleases involved in the normal turnover of mRNA: 5’ to 3’ exonuclease, which is a dependent decapping protein; 3’ to 5’ exonuclease, an independent protein; and poly(A)-specific 3’ to 5’ exonuclease.<ref name">Mukherjee D; et al. (2004). "Analysis of RNA Exonucleolytic Activities in Cellular Extracts". Springer protocols 257: 193–211. doi:10.1385/1-59259-750-5:193. ISBN 1-59259-750-5. PMID 14770007. </ref>

In both archaebacteria and eukaryotes, one of the main routes of RNA degradation is performed by the multi-protein exosome complex, which consists largely of 3' to 5' exoribonucleases.

Significance to polymerase

Spleen exonuclease

Spleen exonuclease (EC 3.1.16.1, 3'-exonuclease, spleen phosphodiesterase, 3'-nucleotide phosphodiesterase, phosphodiesterase II) is an enzyme. This enzyme catalyses the following chemical reaction

This enzyme has a preference for single-stranded substrate.

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Phosphodiesterase I

Phosphodiesterase I (EC 3.1.4.1, 5'-exonuclease, 5'-phosphodiesterase, 5'-nucleotide phosphodiesterase, oligonucleate 5'-nucleotidohydrolase, 5' nucleotide phosphodiesterase/alkaline phosphodiesterase I, 5'-NPDase, 5'-PDase, 5'-PDE, 5'NPDE, alkaline phosphodiesterase, nucleotide pyrophosphatase/phosphodiesterase I, orthophosphoric diester phosphohydrolase, PDE I, phosphodiesterase, exonuclease I) is an enzyme with system name oligonucleotide 5'-nucleotidohydrolase. This enzyme catalyses the following chemical reaction

Hydrolyses both ribonucleotides and deoxyribonucleotides. Has low activity towards polynucleotides.

See also

References

External links