Definition of Exonuclease

Exonuclease is an enzyme that is responsible for digesting the DNA and RNA sequences from either 5’ or 3’ end at one time. Hence, it is a hydrolyzing enzyme which breaks the phosphodiester bonds that are present between the nucleotides. These exonucleases are also present in the snake venom.


This venom breaks that DNA sequence which is responsible for encoding essential proteins in the body. The exonucleases are also required for digesting the RNA primer that is present in the process of transcription. They also help in proofreading and editing the DNA if any error occurs. The exonuclease lacks the defensive property against the entry of pathogens.

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