How are restriction endonuclease named ?

Explanation

The naming of restriction endonuclease is based on the following rules :
(1) The first letter of the REN refers to the genus name of the bacteria from which it is derived and written in capitals.
(2) The second and the third letters refer to the species name of the bacteria from which it is derived, and written in small letters.
(3) If the fourth letter is present it represents the name of the bacterial strain or subspecies.
(4) The Roman number indicates the different REN’s derived from the same organism.