Exonuclease VII

Description:
Exonuclease VII, (Exo VII) derived from E. coli, cleaves single-stranded DNA (ssDNA) from both 5´→3´ and 3´→5´ direction. This enzyme is not active on linear or circular dsDNA. It is useful for removal of single stranded oligonucleotide primers from a completed PCR reaction when different primers are required for subsequent PCR reactions. Digestion of ssDNA by Exonuclease VII is metal-independent.

Applications:

• Removal of single-stranded oligonucleotide primers after PCR
• Removal of terminal phosphorothioated ss-oligonucleotide primers after PCR
• Mapping positions of introns in genomic DNA
• Removal of single-stranded DNA from dsDNA

Source: An E. coli strain that carries cloned Exonuclease VII (XseA and XseB) genes from E. coli.

Unit Definition:
One unit is defined as the amount of enzyme that will catalyze the release of 1 nmol of acid-soluble nucleotide in a total reaction volume of 50 μl in 30 minutes at 37°C. 

Recommended Reaction Conditions: 
1X Exonuclease VII Reaction Buffer
Incubate at 37°C

1X Exonuclease VII Reaction Buffer:
50 mM Tris-HCl
50 mM sodium phosphate
8 mM EDTA
10 mM 2-mercaptoethanol
pH 8 @ 25°C

Recommended Storage Condition:
-20°C  Avoid repeated freeze-thaw.

References:

• Chase, et al. (1974). J. Biol. Chem. 249, 4553-4561.
• Li, H. et al. (1991). Nucl. Acids Res. 19, 3139-3141.