A nuclease that catalyzes the hydrolysis of phosphodiester bond, cleaving a single nucleotide from the end of a polynucleotide chain.
The enzyme may occur as individual enzyme or as part of a larger enzyme complex. For instance, DNA polymerase I has 3′ to 5′ exonuclease activity which is used in editing and proofreading DNA for errors.
Word origin: Greek éxō (outside) + nuclease.
See also: proofreading