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 13485 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.