restriction enzymes

Endonucleases which recognize specific base sequences within a DNAhelix, creating a double-strand break of DNA. Type I restriction enzymes bind to these recognition sites but subsequently cut the DNA at different sites. Type II restriction enzymes both bind and cut within their recognition or target sites.
Source:
PAC, 1992, 64, 143 (Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)) on page 164