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 ?
2002) among various molecular markers technique restriction enzyme based method have been use successfully many year (Jayarao et al.
PCR products of 94 bp were sequenced for SNP detection and incubated with Kpn2I restriction enzyme at 37oC for 15 minutes for genotype determination.
2012) also developed PCR-RFLP methods based on mitochodrial DNA using BseDI restriction enzyme for meat species differention and were able to distinguish the presence of pork in meatballs on a laboratory scale which could detect 0.
Enzyme used for restriction enzyme Hae for this position is able to identify and cut at the (AG / CT) position.
In order to clone in the expression vector plasmid pET-21a was digested with the same two restriction enzymes (NdeI and HindIII) and resolved on agarose gel.
Similarly, the restriction enzymes NlaIV and BsaJI were suitable for discriminating the Indian mud crab species when using the other COI gene fragment (597-bp PCR amplicon produced by the second set of primers).
PFGE was performed according to the PulseNet protocol (CDC/PulseNet with modifications using the ApaI and SmaI restriction enzymes (GRAVES & SWAMINATHAN, 2001).
For integration of the expression cassette into the 18S ribosomal RNA (ssu) locus, the pLEXSY-hyg2 plasmid containing LPG3 gene was digested by SwaI restriction enzyme (Fermentas, Lithuania) and 10 [micro]g of the heavier fragment was transformed into cultivated Lizard Leishmania promastigotes by electroporation in vitro.
We propose a new shape of transition molecules and another kind of restriction enzymes, which cut only when the ligation of a transition molecule to the circular molecule of the input will be accomplished on both sides.
On the other hand when two restriction enzymes were used in combination then incomplete digestion was observed (Fig.
We have also controlled the integrity of the plasmids DNA by generating restriction enzyme profiles for each version of the plasmid and analyzed them on agarose gel.
Restriction enzymes can slow or halt this absorption process.

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