methylated, hydroxymethylated and glucosyl-hydroxymethylated DNA=== Type I ===Type I restriction enzymes were the first to be identified and were first identified in two different strains (K-12 and B) of "E. coli".
Njihovo odkritje je vodilo v razvoj tehnologije rekombinantne DNK, ki na primer omogoča produkcijo humanega inzulina za zdravljene sladkorne bolezni z uporabo bakterije "E. Coli".