Page "Restriction enzyme" Paragraph 11

Naturally occurring restriction endonucleases are categorized into four groups ( Types I, II III, and IV ) based on their composition and enzyme cofactor requirements, the nature of their target sequence, and the position of their DNA cleavage site relative to the target sequence.

All types of enzymes recognise specific short DNA sequences and carry out the endonucleolytic cleavage of DNA to give specific fragments with terminal 5 '- phosphates.

They differ in their recognition sequence, subunit composition, cleavage position, and cofactor requirements, as summarised below: