Nuclease

A nuclease is an enzyme which can cleave nucleic acids at phosphodiester bonds.

Like all enzymes, nucleases are proteins which have an active site for the enzyme reaction and a target molecule recognition site which gives the reaction its specificity.

Nucleases break phosphodiester bonds between nucleotides. There are two types of these enzymes:

• Endonucleases, which create cuts within the DNA or RNA chains themselves and as such create two separate strands;
• and exonucleases which detach nucleotides at the ends of the DNA or RNA chains.

There are also the ribonucleases which only act on ribonucleic acids (RNA), together with the deoxyribonucleases which cleave deoxyribonucleic acid (DNA).

Some nucleases have particular specificity for specific groups of a few nucleotides: these are the restriction enzymes.