gyrase
noun
gyr·ase ˈjī-ˌrās 
: 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
Medical Definition
gyrase
noun
gy·rase ˈjī-ˌrās, -ˌrāz
: 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.