Question

26. Topoisomerases are enzymes that support DNA replication in prokaryotes and eukaryotes. These enzymes have been used as targets for drug development. Answer the following questions on topoisomerases:

(a) What are topoisomerases, what do they do, and how do they support DNA replication? (4 marks)

(b) What is the difference between topoisomerase I and II? (2 marks)

(c) Why is topoisomerase II an attractive drug target for bacterial pathogens? (2 marks)

Answer 1

26. (a) Topoisomerases are enzymes that help in unwinding and relaxing the DNA strands. They untangle DNA strands. These enzymes manage DNA supercoiling. They do so by making a cut/incision in the DNA strand. It helps in unwinding the DNA strand at the time of replication. It helps to gain access to the base pairs by the replicating enzyme DNA polymerase.   

(b) Topoisomerase I is ATP independent enzyme which makes cut in only strand of DNA. Topoisomerase II is ATP dependent enzyme which cuts both the strands of the DNA.

(c) Topoisomerase II is an active drug target for bacterial pathogens because by inhibiting this enzyme DNA replication in pathogenic bacteria can be prevented.