# Do restriction enzymes exist naturally in organisms?

Nov 8, 2017

Yes, that's where they originate from.....

#### Explanation:

Restriction enzymes (RE's) are among the most important tools in the defensive mechanism of bacteria and archaea. They are primarily meant as a defence against invading viral DNA (from bacteriophages like the T-range, M13, $\phi X$174 etc. in the case of E. Coli).

Their own DNA , flowing loosely within the Cytosol, will be vulnerable as well but it will usually be protected from the action of the RE by Methylating a few bases so the RE can't latch on.

NOTE: the attachment site of a RE is not always the Palindromic site itself: some RE's recognise a different region, usually "upstream", where they seem to latch onto the DNA Helix, then make the cut in the Palindromic sequence.

But that is outside the scope of this question....