APPENDIX D Compilation of Commercially Available Nucleases

Abstract

Commercially available nucleases (omitting the restriction endonucleases) have been compiled here in tabular form. The restriction endonucleases are dealt with separately in Appendix A. This appendix was created to assist the researcher in locating a specific biochemical tool for manipulating nucleic acids. The enzymes are divided into five groups.

The Endonucleases table lists various properties of nucleases that act on DNA and RNA (except DNase I, which does not act on RNA). Unlike type II restriction endonucleases, these endonucleases are nonsequence-specific and have varying requirements for strandedness of the DNA and for divalent cation.

The Exonucleases have been useful in manipulating and analyzing DNA and RNA. All of the exonucleases act on DNA molecules. The only two available exonucleases that also act on RNA molecules are phosphodiesterases I and II; they are sugar-nonspecific.

The Homing endonucleases are a relatively newly discovered group of highly sequence-specific deoxyribonucleases. The sequence recognized by these enzymes has proved elusive to define (see Chapter 4). Typically, they cleave DNA less frequently than 1 in 250,000 base pairs on the basis of the number of cleavage sites observed on digestion of bacterial and yeast chromosomal DNA. The sequences presented in the table are those sequences that are the smallest defined “natural” target site for each nuclease.

Most commercially available DNA polymerases contain one or more exonucleolytic activities. The DNA polymerases are included here for completeness.

The Ribonucleases table lists enzymes that exclusively cleave RNA molecules; they all cleave endonucleolytically.

ENDONUCLEASES

PropertiessubstrateEnzymeDNARNAss