Isoschizomer
Encyclopedia
Isoschizomers are pairs of restriction enzyme
Restriction enzyme
A Restriction Enzyme is an enzyme that cuts double-stranded DNA at specific recognition nucleotide sequences known as restriction sites. Such enzymes, found in bacteria and archaea, are thought to have evolved to provide a defense mechanism against invading viruses...

s specific to the same recognition sequence
Recognition sequence
The recognition sequence, sometimes also referred to as recognition site, of any DNA-binding protein motif that exhibits binding specificity, refers to the DNA sequence , to which the domain is specific...

. For example, Sph I (CGTAC/G) and Bbu I (CGTAC/G) are isoschizomers of each other. The first enzyme to recognize and cut a given sequence is known as the prototype, all subsequent enzymes that recognize and cut that sequence are isoschizomers. Isoschizomers are isolated from different strains of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and therefore may require different reaction conditions.

An enzyme that recognizes the same sequence but cuts it differently is a neoschizomer
Neoschizomer
Neoschizomers are restriction enzymes that recognize the same nucleotide sequence as their prototype but cleave at a different site. In some special applications this is a very helpful feature....

. Neoschizomers are a specific type (subset) of Isoschizomers. For example, Sma I (CCC/GGG) and Xma I (C/CCGGG) are neoschizomers of each other.

An enzyme that recognizes slightly different sequence, but produces the same ends is a isocaudomer
Isocaudomer
Isocaudomers are pairs of restriction enzymes that have slightly different recognition sequences but upon cleavage generate identical termini. For example the enzymes Mbo I and BamH I are isocaudomers: Mbo I N*GATC N N CTAG*N BamH I G*GATC C...

.

In some cases, only one out of a pair of isoschizomers can recognize both the methylated as well as unmethylated forms of restriction sites. In contrast, the other restriction enzyme can recognize only the unmethylated form of the restriction site.
This property of some isoschizomers allows identification of methylation state of the restriction site while isolating it from a bacterial strain.
For example, the restriction enzymes HpaII & MspI are isoschizomers, as they both recognize the sequence 5'-CCGG-3' when it is unmethylated. But when the second C of the sequence is methylated, only MspI can recognize both the forms while HpaII cannot.
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