We describe the partial purification and characterisation of five Type II restriction endonucleases from two strains of Herpetosiphon giganteus. One of the activities, HgiJII, was the first enzyme found that cleaves DNA at the family of related sequences 5'-G-R-G-C-Y/C-3'. This enzyme may be related to the enzyme HgiAI from a different strain of the same species, and which cleaves at the sites ...

When searching for the site-specific endonucleases in several strains of Phormidium we made the following observations. Among the 16 strains that originated from 15 species of Phormidium, 12 produced one or more restriction enzymes, of which two produced the highly thermophilic restriction endonucleases PtaI and PpaAII with their optimum activity at 65-80 degrees C, which is far above the letha...