Editing Endonuclease (section)

== Categories ==

Ultimately, there are three categories of [[restriction endonucleases]] that relatively contribute to the cleavage of specific sequences. The types I and III are large multisubunit complexes that include both the [[endonucleases]] and [[methylase]] activities. Type I can cleave at random sites of about 1000 base pairs or more from the recognition sequence and it requires ATP as source of energy. Type II behaves slightly differently and was first isolated by Hamilton Smith in 1970. They are simpler versions of the endonucleases and require no ATP in their degradation processes. Some examples of type II restriction endonucleases include ''Bam''HI, ''Eco''RI, ''Eco''RV, ''Hin''dIII, and ''Hae''III. Type III, however, cleaves the DNA at about 25 base pairs from the recognition sequence and also requires ATP in the process.<ref name="Cox_Nelson_Lehninger_2005"/>