Restriction enzyme

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Restriction enzyme

An enzyme, specifically an endode-oxyribonuclease, that recognizes a short specific sequence within a deoxyribonucleic acid (DNA) molecule and then catalyzes double-strand cleavage of that molecule. Restriction enzymes have been found only in bacteria, where they serve to protect the bacterium from the deleterious effects of foreign DNA. See Deoxyribonucleic acid (DNA)

There are three known types of restriction enzymes. Type I enzymes recognize a specific sequence on DNA, but cleave the DNA chain at random locations with respect to this sequence. They have an absolute requirement for the cofactors adenosine triphosphate (ATP) and S-adenosylmethionine. Because of the random nature of the cleavage, the products are a heterogeneous array of DNA fragments. Type II enzymes also recognize a specific nucleotide sequence but differ from the type I enzymes in that they do not require cofactors and they cleave specifically within or close to the recognition sequence, thus generating a specific set of fragments. It is this exquisite specificity which has made these enzymes of great importance in DNA research, especially in the production of recombinant DNAs. Type III enzymes have properties intermediate between those of the type I and type II enzymes. They recognize a specific sequence and cleave specifically a short distance away from the recognition sequence. They have an absolute requirement for the ATP cofactor, but they do not hydrolyze it.

A key feature of the fragments produced by restriction enzymes is that when mixed in the presence of the enzyme DNA ligase, the fragments can be rejoined. Should the new fragment carry genetic information that can be interpreted by the bacterial cell containing the recombinant molecule, then the information will be expressed as a protein and the bacterial cell will serve as an ideal source from which to obtain that protein. For instance, if the DNA fragment carries the genetic information encoding the hormone insulin, the bacterial cell carrying that fragment will produce insulin. By using this method, the human gene for insulin has been cloned into bacterial cells and used for the commercial production of human insulin. The potential impact of this technology forms the basis of the genetic engineering industry. See Enzyme, Genetic engineering

References in periodicals archive ?
At 10 and 24 hpf, gDNA extracted from TDCPP-treated embryos was incompletely digested by all methylation-sensitive restriction endonucleases tested, and banding patterns were similar to those of vehicle-treated controls (Figure 6).
A cladistic analysis of phenotypic associations with haplotypes inferred from restriction endonuclease mapping and DNA sequence data.
2008) greatly facilitated optimization of the key by allowing us to perform virtual restriction endonuclease digestion (VRED) analyses, which saved time by eliminating much of the laboratory-intense trial-and-error usually associated with identifying informative restriction endonucleases.
Although their existence had been hypothesised almost twenty years earlier, (23,24) the first restriction endonucleases were not isolated until 1968.
Use of low-frequency-clevage restriction endonucleases for DNA analysis in epidemiological investigations of nosocomial bacterial infections.
In this case, methylation analysis involving the use of methylation-sensitive restriction endonucleases could be used, thus cutting hypomethylated RASSF1A from maternal blood cells and leaving the hypommethylated placental RASSF1A intact for amplification.
Polysaccharide contaminations are particularly problematic as they inhibit the activity of many commonly used molecular biological enzymes, such as polymerases, ligases and restriction endonucleases [3].
Restriction enzymes, also known as restriction endonucleases, are a group of enzymes that cleave DNA molecules at specific sites.
These include restriction endonucleases for cleaving DNA and ligases for joining the fragments, recombinases that can execute a large variety of DNA cleavage and joining reactions.
7 kb) of DNA by the polymerase chain reaction and subsequent digestion with informative restriction endonucleases.
19,20) Kits modeled on RFLP use restriction endonucleases specific for sites that confer the variation between alleles.

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