The Restriction Enzyme data BASE is a collection of information about restriction enzymes and related proteins. It is maintained by New England Biolabs. It contains published and unpublished references, recognition and cleavage sites, isoschizomers, commercial availability, methylation sensitivity, crystal and sequence data. DNA methyltransferases, homing endonucleases, nicking enzymes, specificity subunits and control proteins are also included. More recently, putative DNA methyltransferases and restriction enzymes, as predicted from analysis of genomic sequences, are also listed.