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Topoisomerase I human

buffered aqueous glycerol solution, ≥2 units/μL

DNA Topoisomerase I
Enzyme Commission number:
MDL number:


expressed in baculovirus

Quality Level


buffered aqueous glycerol solution

mol wt

100 kDa


≥2 units/μL

UniProt accession no.

storage temp.


Gene Information

human ... TOP1(7150)

General description

Topoisomerase I (TOP1) is mapped to human chromosome 20q12.[1] TOP1 is a 91 kDa type IB enzyme and consists of N-terminal highly charged domain, a core, linker domain and a C-terminal catalytic domain with Tyr-723 active site residue.[2]


Topoisomerase I has been used in a study to assess implications for the regulation of HIV-1 replication. [3] Topoisomerase I has also been used in a study to investigate the tumor suppressor protein kinase Chk2 is a mediator of anoikis of intestinal epithelial cells. [4]
Topoisomerase I human has been used for Topoisomerase I assay for screening inhibitors.[5]

Biochem/physiol Actions

Topoisomerase I human (TOP1) interacts with DNA by wrapping and takes a bi-lobed conformation.[2] TOPI is essential for normal development and transcriptional regulation.[6] Variants in the TOP1 gene is observed in patients with colorectal cancer.[1]
Topoisomerase I relaxes supercoiled DNA molecules. The enzyme initiates transient breakages and rejoins of phosphodiester bonds in superhelical turns of closed-circular DNA. Enzyme activity is independent of right- and left-handed superhelices.

Unit Definition

One unit will relax 0.25 μg of supercoiled plasmid DNA in 30 minutes at pH 7.9 at 37 °C.

Physical form

Solution containing 20 mM sodium phosphate, pH 7.4, 300 mM NaCl, 50 μg/mL BSA, 50% glycerol, and between 25-100 mM imidazole (concentration will be lot dependent).


Health hazard

Signal Word


Hazard Statements

Precautionary Statements

Hazard Classifications

Repr. 1B

Storage Class Code

6.1D - Non-combustible, acute toxic Cat.3 / toxic hazardous materials or hazardous materials causing chronic effects



Flash Point(F)

Not applicable

Flash Point(C)

Not applicable

Certificate of Analysis

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Certificate of Origin

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