Enzyme systems composed of two subunits and requiring ATP and magnesium for endonucleolytic activity; they do not function as ATPases. They exist as complexes with modification methylases of similar specificity listed under EC 2.1.1.72 or EC 2.1.1.73. The systems recognize specific short DNA sequences and cleave a short distance, about 24 to 27 bases, away from the recognition sequence to give specific double-stranded fragments with terminal 5'-phosphates. Enzymes from different microorganisms with the same specificity are called isoschizomers. EC 3.1.21.5.

Synonyms: EC 3.1.21.5, Type III Restriction Enzymes, Type III Site-Specific Deoxyribonucleases, Deoxyribonucleases, Type III Site-Specific, Deoxyribonucleases, Type III, Site-Specific, Type III Site-Specific DNase, DNase, Site-Specific, Type III, Restriction Endonucleases, Type III, DNA Restriction Enzymes, Type III, Type III Site Specific Deoxyribonucleases, DNase, Site Specific, Type III, Deoxyribonucleases, Type III, Site Specific, Site Specific DNase, Type III, Deoxyribonucleases, Type III Site Specific, Type III Site Specific DNase, Site-Specific DNase, Type III