Restriction enzymes are those enzyme which are present in bacterial cells as a defence mechanism to restrict the growth of bacteriophage, by cutting the DNA at specific sites.
The first letter of the name comes from the genus of the prokaryote.
The second and third letters come from the name of the species of the cell from where it is obtained.
The fourth letter comes from the strain of the prokaryote.
The Roman numbers following these 4 letters indicate the order in which enzymes were isolated from the strain of the bacterise.
e.g. E Coli RI is isolated from Escherichia coli strain RY13. The letter ‘R” stands for the strain.
