Difference between Helicase and Topoisomerase


Helicases are enzymes that separate nucleic acid strands, such as dsDNA, DNA-RNA hybrid, and self annealed RNAs. They utilise energy by the hydrolysis of nucleoside triphosphates to motor through the strands. They separate the strands by breaking the hydrogen bonds between nucleotide bases.

The helicases can be categorised into six superfamilies. SF1, SF2 and SF3 are large families and SF4, SF5 and SF6 are small families. The helicases function to separate the strands for replication, recombination, repair, transcription and translation.


Topoisomerases are enzymes that release the tension in DNA strands. When a DNA strand undergoes replication or transcription, the strand that is ahead of the replication fork starts to owerwind. If the overwinding is not detangled, the torsion in the DNA strands will destroy the strand and render it non-functional.

In simple words, topoisomerases maintain the overall topology of DNA strands. The enzymes work by binding to the DNA strands and breaking the phosphate bond of either one or both strands. This allows the DNA to untangle and then the ends are again resealed. They do not require any energy for this process.

Now that we know about Helicases and Topoisomerases in brief, let us look at the table of differences below.




Helicases are enzymes that separate the nucleic acid strands for replication.

Topoisomerases are enzymes that relax the supercoiling in DNA strands.

Energy Requirement

It utilises energy from the hydrolysis of nucleoside triphosphates to translocate through the DNA strands.

Topoisomerase I does not utilise energy, but Topoisomerase II does as it cuts both strands in DNA.


It is divided into 6 superfamilies.

Type I and type II

Breaking of Bonds

It breaks the hydrogen bonds between the nucleotide bases.

It breaks the phosphate backbone of either one or both strands to detangle the DNA strands.


It separates both double-stranded DNA and self annealed RNA strands.

It unwinds DNA only.


It separates the DNA or RNA strands for replication and recombination.

It maintains the overall topology of the DNA strands.


DNA helicase and RNA helicase.

Topoisomerase I and Topoisomerase II.

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Frequently Asked Questions


What is DNA topology?

The tertiary structure of DNA is referred to as DNA topology.


What are the topological problems that DNAs face?

Catenation, supercoiling and knotting in the strands are the topological problems commonly found in DNAs.


What is the difference between helicase and gyrase?

Helicases are enzymes that separate nucleic acid strands. On the other hand, gyrases belong to the family of topoisomerase II that maintains the topology of DNA strands.


What is the difference between topoisomerase I and II?

Type I topoisomerases break only one strand of DNA, whereas type II topoisomerases break both strands of DNA.


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