Difference Between Endonuclease and Exonuclease

Nucleases play an indispensable role in recombinant DNA technology, genetics, and genetic engineering. Because of their ability to cut DNA segments, nucleases have various practical applications.

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Endonuclease vs Exonuclease

The difference between endonuclease and exonuclease is that an endonuclease is a group of enzymes that cuts DNA segments from the inner side. On the other hand, exonuclease enzymes cut DNA segments from the ends. Additionally, endonuclease enzymes have either sticky or blunt ends. In contrast, exonuclease enzymes have sticky ends. 

Endonuclease vs

Its function is to cut the DNA segment at its recognition site. More importantly, endonuclease enzymes cut the DNA segment from the inner side. 

The most vital application of exonuclease is to assist in DNA repair. More importantly, exonuclease enzymes cut DNA segments from the ends. 

Comparison Table

Parameters of ComparisonEndonuclease Exonuclease 
DefinitionEndonuclease refers to the group of enzymes that cut the DNA segments from the inner side. Exonuclease refers to the group of enzymes that cut the DNA segment from the ends. 
Lag PeriodEndonucleases, like the restriction endonuclease, experience a lag period before carrying out their specific task. In exonucleases, there is an absence of lag period before the commencement of their specific task. 
Results InThe cleaving of DNA segments results in oligonucleotides. The cleaving of DNA segments results in nucleosides.  
FunctionEndonuclease enzymes play a role in defense as they prevent the entry of pathogens.Exonucleases lack any defensive functions. 
Free EndsEndonuclease enzymes don’t require free 3’ and 5’ ends to perform their functions. Exonucleases require free ends for the commencement of their specific tasks. 

What is Endonuclease?

Endonuclease refers to the group of enzymes found within the polynucleotide chain which cleave the phosphodiester bond.  Some endonuclease enzymes, for instance, deoxyribonuclease I, cut the Deoxyribonucleic acid without any regard to sequence.

One of the most vital groups of endonucleases is the restriction enzymes. The restriction enzymes have three categories based on their action mechanism: Type I, Type II, and Type III. 

Bacterial cells are the natural source of restriction endonuclease. Moreover, the ends of endonucleases are either blunt or sticky. An example of a famous endonuclease is Cas9.

Endonucleases are vital for several reasons. However, one of the more prominent reasons is their ability to repair damaged DNA cells precisely.

What is Exonuclease?

Exonucleases refer to the group of enzymes that function by cutting nucleotides one at a time from the Exo (end) of a polynucleotide chain. These enzymes cut the nucleotide from either the 3’ or the 5’ at one specific time. Additionally, exonuclease serves as a hydrolyzing enzyme.

Exonuclease is found in humans, bacteria, animals, and insects. Interestingly, the venom of lizards and snakes consists of exonuclease enzymes. 

Exonuclease enzymes play a vital role in cellular metabolism and maintenance. Moreover, they are crucial aspects of genome stability as they cut the DNA from free ends. Exonucleases may also have a part in repairing damaged DNA cells.

In the case of exonuclease enzymes, the lag period is absent before activity. Conclusively, exonucleases are a group of enzymes serving multi-facet functions. 

Main Differences Between Endonuclease and Exonuclease

  1. Endonucleases, like the restriction endonuclease, experience a lag period before carrying out their specific task. On the other hand, in exonucleases, the lag period is absent before the commencement of their specific task. 
  2. Endonuclease enzymes don’t require free 3’ and 5’ ends to perform their functions. In contrast, exonucleases require free ends for the commencement of their specific tasks. 

References

  1. https://www.tandfonline.com/doi/abs/10.3109/10409237609105456 
  2. https://www.pnas.org/content/68/4/824.short 
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