Klenow Fragment exo- (3’→5′ exo-)

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Klenow Fragment exo- (3’→5′ exo-) is a product of E. coli DNA Polymerase I which lacks the N-terminal 324 amino acids. This enzyme lacks the 5’→ 3′ exonuclease activity of intact DNA Polymerase I, and has mutations (D355A, E357A) which abolish the 3´→ 5´ exonuclease activity but does exhibit the 5’→ 3′ DNA polymerase activity (1). These characteristics make the enzyme useful for several molecular biology applications such as:

  • Recombinase polymerase amplification (RPA) assay
  • Di-deoxy sequencing (2)
  • Second strand cDNA synthesis
  • Second strand synthesis in mutagenesis (3)
  • Single-stranded DNA probes generation


Protein Purity
The physical purity of this enzyme is ≥99% as assessed by SDS-PAGE with Coomassie® blue staining.

Product Includes
Klenow Fragment exo-
10x Klenow exo- reaction buffer

Storage temperature

Storage Buffer
50 mM Tris-HCl (pH 7.5), 0.1 mM EDTA, 1 mM β-mercaptoethanol, 1 mM DTT and 50% (v/v) glycerol.

Unit Definition
One unit is defined as the amount of enzyme that will incorpo-rate 10 nmol of dNTP into acid-insoluble material in 30 minutes at 37°C under standard assay conditions.

10x Reaction Buffer
500 mM Tris-HCl, 100 mM MgCl2, 50 mM dithiothreitol (DTT), pH 7.5 @ 25°C.

Product Source
E. coli cells carrying E. coli polA gene without its N-terminal exonuclease domain and carry D355A/E357A mutations.

Inactivated by heating at 75°C for 20 min.

Quality Control Assays
DNA Polymerase I, Klenow Fragment exo- is free from detect-able endonuclease and RNase activities.

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1 Review

  • 5

    Posted by Liam on 4th Dec 2021

    Having received the product so quickly was really surprising to me. I'll definitely order this item again

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