What are Topoisomerases? Where are they present?

Topoisomerase Enzymes are enzymes that are part of the DNA replication process.

These enzymes help breaking the bonds between two strands of DNA and unwind the double helix structure. These enzymes are also used to attach a terminal protein to a strand of DNA or by adding an extra strand of DNA.

Although these enzymes are good for the replication of DNA, they are also used to break down the DNA of a virus. This is because of their target is the virus.

Topoisomerase enzyme structure Topoisomerase Enzyme structure

Each DNA virus has a protein capsid that has double stranded DNA within. Because of this, the enzyme binds to the protein layer and breaks down the strand of DNA that is within the capsid.

Because of this, the virus will be broken down and used for the purpose of the body. Topoisomerase is present in all living organisms.

Topoisomerase enzymes are present in most of the cells of the body, however some viruses have found a way to incorporate them into their genome.

It used by viruses that cause diseases such as HIV and hepatitis.


  1. Topoisomerases are enzymes that \”untangle\” DNA by changing the shape of a double helix. Topoisomers are enzymes which can change the shape of DNA. It is present in bacteria, eukaryotes and viruses to change the shape of the DNA. It is a part of the bacterial DNA repair mechanisms and also present in bacterial plasmids.

  2. Topoisomerase is a homodimeric chromosomal unwinding enzyme that creates a double-stranded nick in DNA, enabling the unwinding required for replication and re-ligation.

    Topoisomerase inhibition prevents cell division, which is the goal of a number of chemotherapeutic drugs (e.g., etoposide).

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