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Thermo Scientific™ Exonuclease I (Exo I)

Degrade single-stranded DNA in a 3'→5' direction with Exonuclease I (ExoI), leaving 5'-terminal dinucleotides intact.

Manufacturer: thermo scientific™  EN0581

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The purchase of this product allows the purchaser to use it for preparing amplified DNA fragments under a license from GE Healthcare of U.S. Patent Nos. 5,741,676 and 5,756,285 and other foreign patents.

Catalog No. FEREN0581


Description & Specifications


Concentration 20U/µL
Inhibitors 20% (w/v) PEG 8000 (5)
Source E.coli cells with a cloned E.coli sbcB gene
Molecular Weight 54.5kDa monomer
Units 4,000U

Exonuclease I (ExoI) degrades single-stranded DNA in a 3'=>5' direction. It releases deoxyribonucleoside 5'-monophosphates in a stepwise manner and leaves 5'-terminal dinucleotides intact.

It does not cleave DNA strands with terminal 3'-OH groups blocked by phosphoryl or acetyl groups.


  • Active in PCR buffers


  • Primer removal from PCR mixtures:
    • prior to PCR product sequencing
    • li>for one-tube "megaprimer" PCR mutagenesis
  • Removal of single-stranded DNA containing a 3'-hydroxyl terminus from nucleic acid mixtures
  • Assay for the presence of single-stranded DNA with a 3'-hydroxyl terminus


The enzyme is not suitable for removing 3'-overhangs of dsDNA.