A class of enzymes that cleave (i.e. cut) DNA at a specific and unique internal location along its length. These enzymes are naturally produced by bacteria that use them as a defense mechanism against viral infection. The enzymes chop up the viral nucleic acids and hence their function is destroyed. Discovered in the late 1970s by Werner Arber, Hamilton Smith, and Daniel Nathans, restriction endonucleases are an important tool in genetic engineering, enabling the biotechnologist to splice new genes into the location(s) of a molecule of DNA where a restriction endonuclease has created a gap (via cleavage of the DNA).
One of many bacterial enzymes that inactivates foreign DNA but does not interfere with the cell’s DNA. This type of enzyme is used to cleave strands of DNA at specific sites.