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Certain enzymes cut DNA (deoxyribonucleic acid) molecules at specific sites to produce DNA fragments. The site of cleavage is called the restriction site, and such enzymes are called restriction enzymes or endonucleases.

The restriction enzymes are found in bacteria, and hundreds of such enzymes have been isolated from different strains of bacteria. Because of their property to recognize and cut specific nucleotide sequences on DNA, they are widely used as a molecular tool in recombinant DNA technology.

PvuI is one such restriction enzyme that is obtained from the bacteria Proteus vulgaris. It recognizes six base pair long restriction sites, 5鈥�-CGATCG-3' on each strand, and cleaves between the T and C on both strands of DNA.

PvuIrecognizes its restriction site, 5鈥�-CGATCG-3', and cleaves the phosphodiester bond present between the 3'OH group of thymine and the 5' phosphate group of the cytosine.

Thus, the enzyme cleaves the covalent sugar-phosphate formed between the thymine and cytosine on both strands.