Escherichia coli restriction enzymes

Restriction enzymes are named after the bacterium from which they are isolated. For example, EcoRI is from Escherichia coli, and BamEII is from Bacillus amyloliquefaciens (Table 40-2). The first three letters in the restriction enzyme name consist of the first letter of the genus (E) and the first two letters of the species (co). These may be followed by a strain designation (R) and a roman numeral (I) to indicate the order of discov-ery (eg, EcoRI, EcoRIE). Each enzyme recognizes and cleaves a specific double-stranded DNA sequence that is 4—7 bp long. These DNA cuts result in blunt ends (eg,... 

Every restriction enzyme recognizes and cuts a specific DNA sequence which usually consists of four or six nucleotide pairs. For example, a restriction endonuclease Eco RI obtained from Escherichia coli cuts wherever it encounters the nucleotide sequence GAATTC, whereas Bal 1 from... 

Oxyrase.. We must also consider the Oxyrase svstem for o.xvgen removal. This is presently derived from Escherichia coli or Bacillus subtil is, but could be derived from other sources too, such as various yeasts (J. Copeland, Oxyrase Inc., personal communication), making the system potentially suitable for use in foods. Because of the diversity of enzymes in this system, the presence of such substrates as lactic acid, succinic acid, formic acid, or a-glveerophosphate, tound in virtually any biological tissue, can effect deoxygenation and attendant stabilization or restriction on 1 he growth of aerobic oiganisms. 

Hydantoinase-Carbamoylase System for t-Amino Acid Synthesis Despite a number of reports of strains with L-selechve hydantoin-hydrolyzing enzymes [38] the commercial application of the hydantoinase process is stiU restricted to the production of D-amino acids. Processes for the production of L-amino acids are Umited by low space-time yields and high biocatalyst costs. Recently, a new generation of an L-hydantoinase process was developed based on a tailor-made recombinant whole cell biocatalyst. Further reduction of biocatalyst cost by use of recombinant Escherichia coli cells overexpressing hydantoinase, carbamoylase, and hydantoin racemase from Arthrohacter sp. DSM 9771 were achieved. To improve the hydan-toin-converting pathway, the level of expression of the different genes was balanced on the basis of their specific activities. The system has been appUed to the preparation of L-methionine the space-time yield is however still Umited [39]. Improvements in the deracemization process from rac-5-substituted hydantoins to L-amino acids still requires a more selective L-hydantoinase. 

More than 100 restriction enzymes have been purified and characterized. Their names consist of a three-letter abbreviation for the host organism (e.g., Eco for Escherichia coli, ERn for Haemophilus influenzae, Hae for Haemophilus... 

Figure 7 Cloning by restriction digest and ligation. Both the PCR-amplified gene of interest and the target vector are digested with the same restriction enzymes (or with enzymes that produce compatible ends). The short section of overhanging sequence (called sticky ends ) are complementary to each other. The digested DNAs are mixed, treated with ligase, and transformed into a suitable Escherichia coli host strain to produce a new recombinant DNA molecule with the gene of interest specifically inserted into a host vector.

Several hundred restriction enzymes have been purified and characterized. Their names consist of a three-letter abbreviation for the host organism (e.g., Eco for Escherichia coli, Hin for Haemophilus influenzae, Mae for Haemophilus aegyptius) followed by a strain designation (if needed) and a roman numeral (if more than one restriction enzyme from the same strain has been identified). The specificities of several of these enzymes are shown in Figure 5.1. 

Tan, X., Suzuki, N., Grollman, A.P., and Shibutani, S. (2002) Mutagenic events in Escherichia coli and mammalian cells generated in response to acetylaminofluorene-derived DNA adducts positioned in the Narl restriction enzyme site. Biochemistry, 41, 14255-14262. 

The first type of DNA fragment is a dsDNA fragment prepared by the restriction enzyme digestion of plasmid DNA isolated from Escherichia coli. In contrast to in vitro DNA synthesis (PGR), DNA replication in living cells is quite accurate... 

The names of restriction enzymes are derived from their bacterial sources. One of the enzymes most widely used in recombinant DNA work is oRl, which is isolated from Escherichia coli RY13. Other examples include Hindu (isolated from Haemophilus influenza Rd), and Xba I (isolated from Xanthmtonas badrO). The specificity of each enzyme allows researchers to cut DNA in a predictable and reproducible manner. Using oRl on the above sequence, one would always obtain the ends ... 

Restriction enzymes are named for the baoterium from which they were isolated (e.g., ECO is from Escherichia coli.). 

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