EC - Type III site-specific deoxyribonuclease

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IntEnz Enzyme Nomenclature


Accepted name:
type III site-specific deoxyribonuclease
Other names:
restriction-modification system
type III restriction enzyme
Systematic name:



This is a large group of enzymes which, together with those now listed as EC (type I site-specific deoxyribonuclease) and EC (type II site-specific deoxyribonuclease), were previously listed separately in sub-subclasses EC 3.1.23 and EC 3.1.24. They have an absolute requirement for ATP but do not hydrolyse it; S-adenosy-L-methionine stimulates the reaction, but is not absolutely required. They recognize specific, short DNA sequences and cleave a short distance away from the recognition sequence. These enzymes exist as complexes with enzymes of similar specificity listed under EC [site-specific DNA-methyltransferase (adenine-specific)] or EC [site-specific DNA-methyltransferase (cytosine-specific)]. A complete listing of all of these enzymes has been produced by R.J. Roberts and is available at

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0015668
CAS Registry Number: 9075-08-5 (not distinguished from EC


  1. Roberts, R.J.
    Restriction enzymes and their isoschizomers.
    Nucleic Acids Res. 18 : 2331-2365 (1990). [PMID: 2159140]
  2. Roberts, R.J. and Macelis, D.
    REBASE—restriction enzymes and methylases.
    Nucleic Acids Res. 29 : 268-269 (2001). [PMID: 11125108]
  3. Roberts, R.J., Belfort, M., Bestor, T., Bhagwat, A.S., Bickle, T.A., Bitinaite, J., Blumenthal, R.M., Degtyarev, S.Kh., Dryden, D.T., Dybvig, K., Firman, K., Gromova, E.S., Gumport, R.I., Halford, S.E., Hattman, S., Heitman, J., Hornby, D.P., Janulaitis, A., Jeltsch, A., Josephsen, J., Kiss, A., Klaenhammer, T.R., Kobayashi, I., Kong, H., Krüger, D.H., Lacks, S., Marinus, M.G., Miyahara, M., Morgan, R.D., Murray, N.E., Nagaraja, V., Piekarowicz, A., Pingoud, A., Raleigh, E., Rao, D.N., Reich, N., Repin, V.E., Selker, E.U., Shaw, P.C., Stein, D.C., Stoddard, B.L., Szybalski, W., Trautner, T.A., Van Etten, J.L., Vitor, J.M., Wilson, G.G. and Xu, S.Y.
    A nomenclature for restriction enzymes, DNA methyltransferases, homing endonucleases and their genes.
    Nucleic Acids Res. 31 : 1805-1812 (2003). [PMID: 12654995]

[EC created 1984 from EC 3.1.23 and EC 3.1.24]