gyrase

noun

gyr·​ase ˈjī-ˌrās How to pronounce gyrase (audio)
: a bacterial enzyme that catalyzes the breaking and rejoining of bonds linking adjacent nucleotides in circular DNA to generate supercoiled DNA helices

Word History

Etymology

gyr- + -ase

First Known Use

1976, in the meaning defined above

Time Traveler
The first known use of gyrase was in 1976

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Cite this Entry

“Gyrase.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/gyrase. Accessed 4 Feb. 2026.

Medical Definition

gyrase

noun
: a bacterial enzyme that is a topoisomerase which catalyzes the ATP-dependent breaking and rejoining of double-strands in circular DNA to generate negative supercoils that twist in the opposite direction as the turns in the original helices

Note: The supercoils introduced by the bacterial gyrase help to relieve the torsional stress in the circular DNA strands that is a consequence of the unwinding of the DNA during replication.

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