Table 3.
The number of restriction enzymes, both confirmed and putative, in REBASE as at April 2018. The numbers were derived by simply counting the number of R subunits for the Type I RM systems, the number of REases for the Type II systems and Type IV systems and the number of res subunits for the Type III RM systems. The proportions are very similar to those obtained previously by Oliviera et al., (5)
| RM system | Number of examples | Percentage of total | Percentage of total ignoring Type IV |
|---|---|---|---|
| Type I REase | 18580 | 26.6 | 31.8 |
| Type IIP REase | 13648 | 19.6 | 23.4 |
| Type II REase (not IIP or IIG) | 7144 | 10.2 | 12.2 |
| Type IIG REase/MTase | 11737 | 16.8 | 20.1 |
| Type III REase | 7305 | 10.5 | 12.5 |
| Type IV REase | 11356 | 16.3 | - |
| Total | 69770 | 100 | 100 |