Definition of Topoisomerase
Topoisomerase: A class of enzymes that alter the supercoiling of double-stranded DNA. (In supercoiling the DNA molecule coils up like a telephone cord, which shortens the molecule.) The topoisomerases act by transiently cutting one or both strands of the DNA. Topoisomerase type I cuts one strand whereas topoisomerase type II cuts both strands of the DNA to relax the coil and extend the DNA molecule.
The regulation of DNA supercoiling is essential to DNA transcription and replication, when the DNA helix must unwind to permit the proper function of the enzymatic machinery involved in these processes. Topoisomerases serve to maintain both the transcription and replication of DNA.
Aside from topoisomerases I and II, there are more discovered topoisomerases. Topoisomerase III may regulate recombination while topoisomerase IV regulates the process of segregating newly replicated chromosomes from one another.Source: MedTerms™ Medical Dictionary
Last Editorial Review: 5/13/2016
Top RxList Drug News
- First US Case of E coli Resistant to Last-Resort Antibiotic
- FDA Approves Afstyla for Adults, Children With Hemophilia A
- FDA Approves New Diagnostic Imaging Agent to Detect Recurrent Prostate Cancer
- Drug Targeting Blood-Brain Barrier 'Hopeful' in Stroke
- FDA Approves Probuphine Implant for Opioid Dependence