Figure 1. Comparison of inactivation properties of HL-ExoI and a commercial E.coli ExoI (EcExoI). After incubation for 10 min the nucleases were inactivated at 60°C for 15 min. The samples were then added a Fam labeled 20-mer and incubated for 30 min before visualization on a urea-PAGE gel.


HL-ExoI is a 3’-5’ exonuclease, specific for single stranded DNA. HL-ExoI is active at temperatures ≥25°C, and inactivated by 1 min incubation at 80°C, or 15 min at 60°C.


Source: Recombinantly produced in an E. coli strain expressing the HL-ExoI gene originating from an Arctic marine bacterium.

Unit Definition: One unit catalyses the release of 10 nmol of acid soluble nucleotides in 30 min at 25°C. Reaction buffer: 20 mM Tris-HCl pH 7.5 at 25°C, 200 mM NaCl, 20 mM MgCl2, 1 mM DTT, 0.01% Triton X-100, 2.5% glycerol and 3H-dATP-labelled DNA (25 ng/µl).

Optimal reaction conditions: 0-15 mM MgCl2 and ≤100 mM NaCl, at 25-37°C.

Storage and Stability

The enzyme is stable at -20°C for 2 years in the supplied storage buffer. The enzyme tolerates at least five freeze-thaw cycles (-80°C) without loss of activity.

Quality Control

ArcticZymes is dedicated to the quality of our products. We manufacture all our products at our ISO:9001 certified facility in Norway

ssDNA endonuclease activity: 100 U HL-ExoI was incubated with M13 ssDNA (0.5 μg) for 4 hours at 37°C. Agarose gel electrophoresis did not reveal any visible signs of ssDNA degradation.

dsDNA endonuclease activity: 200 U HL-ExoI was incubated with a supercoiled plasmid (1 μg) for 4 hours at 37°C. Agarose gel electrophoresis did not reveal any transformation of closed circular DNA to nicked DNA.

Additional Data and Information

We are pleased to provide data and information relating to HL-Exol. The Product is an Early Access Product, and further product information will be generated continuously. We appreciate suggestions for product modifications.