Fuente: WIPO "tobacco agriculture" The invention discloses adenosine monophosphate enzyme as well as a preparation method and an application thereof, including an expression vector of adenosine monophosphate enzyme, a preparation method of the adenosine monophosphate enzyme, an application of the adenosine monophosphate enzyme in in-vitro adenosine monophosphate modification of subunit GyrB and ParE proteins of DNA topoisomerase, and an application of the adenosine monophosphate enzyme in in-vitro inhibition of ATP hydrolysis activity of the DNA topoisomerase, and in inhibition of DNA topoisomerase negative superhelix and relaxation of DNA activity. The preparation method of the adenosine monophosphate enzyme provided by the invention is simple, short in fermentation period, low in purification cost and large in preparation amount; by utilizing the adenosine monophosphate enzyme provided by the invention, adenosine monophosphate modification of the DNA topoisomerase can be realized under an in-vitro condition; the adenosine monophosphate enzyme provided by the invention is expressed, the activity of DNA topoisomerase can be inhibited.