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 ?
We did not perform restriction enzyme analysis on the isolate from the patient sample suspected to be co-infected with HAdV-E4 and HAdV-B14.
ARDRA has proved to be useful for the differentiation of bacterial strains at different taxonomic levels, depending on selection of conserved or variable regions followed by digestion using tetracutter restriction enzymes in the ribosomal genes.
Table 3-4 - polymorphic position size and details bands digested by restriction enzyme Hae
DNA restriction enzymes DNA polymerase DNA extraction kit InsTA PCR cloning kit and GeneJET Plasmid Miniprep kit were purchased from Thermo Scintific.
The restriction endonucleases AseI, MaeI, MboII, TaqI, and BsmAI were selected for the first PCR product (for the 709-bp amplified product using primers LCO1490 and HC02198), and the restriction enzymes BsaJI, NlaIV, MaeII, TfiI, and BfaI were selected for the second product (for the 597-bp amplified product using primers rntd-10 and C/N-2769) based on the best discrimination and species-specific amplicon patterns.
Digestion with HPA 2 restriction enzyme produced 2 bands 209 bp and 99 bp indicating both alleles have G polymorphs which are true with sample number 157 of which undigested and digested products are shown in lane 4 and 5 respectively.
The hyg2-LPG3 fragment containing one copy of the LPG3 obtained from the digestion of pLEXSY-LPG3 with the SwaI restriction enzyme was used for integration into the small subunit of Lizard Leishmania rRNA gene for homologous recombination by electroporation.
0], A [perpendicular]) which pushes the symbol A on the stack is to use the restriction enzyme Bg/I, which cuts the DNA strand only when the transition molecule merges the stack and the input tape.

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