exonuclease
An enzyme that works by cleaving nucleotides one at a time from the end of a polynucleotide chain (e.g. DNA, RNA). A hydrolyzing reaction that breaks phosphodiester bonds at either the 3' or 5' end occurs.
(Types)
• 3' -› 5' exonuclease
• 5' -› 3' exonuclease
• bidirectional exonuclease
(Functions)
• RNA degradation
• RNA turnover
• DNA proofreading (error-correcting processes)
• transcriptional regulation (conversion of DNA to RNA)
(Comparison)
• exonuclease (exo = outer, external): Cleaves nucleotides from the end of the polynucleotide chain.
• endonuclease (endo = inner, internal): Cleaves nucleotides in the middle of the polynucleotide chain.