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 ?
Restriction enzyme digest fragment profiles generated during this study matched exactly those expected for Scylla serrata and Scylla olivacea (Table 5).
enterica serotype I,4,[5],12:i- infections (pulsed-field gel electrophoresis XbaI restriction enzyme pattern JPXX01.
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.
Thus, tens of thousands of target regions can be analyzed simultaneously, using as little as 50 ng of input DNA, with very high coverage, due to the restriction enzyme digestion approach.
Identification of this mutation by PCR based restriction enzyme digestion of that fragment of p85a gene which contained the Msp1 site is the background of this study.
created by HpyCh4IV digestion, it created a site for the relatively rare-cutting restriction enzyme, MluI (New England Biolabs).
Then introduce the concept that a restriction enzyme works by "chopping" DNA into smaller pieces (restriction enzymes can be thought of as "scissors" that cut DNA).
Restriction enzyme digestion of the isolated plasmid was carried out by incubating the reaction mixture in a water bath at 37[degrees]C for 3 hours and deactivated in 65[degrees]C for 20 minutes.
Restriction digests were performed with the purified PCR product in a 40 [micro]L reaction with approximately 1200 ng of DNA (24 [micro]L), 2 [micro]L of restriction enzyme, 4 [micro]L of restriction enzyme 10X buffer, and 10 [micro]L of sterile mili-Q distilled [H.

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