DNA旋转酶(DNA Gyrase)，经常简称为旋转酶，是一种II类的拓扑异构酶（Type II Topoisomerase）（EC编号5.99.1.3），它的酶作用底物为ccc型环状DNA（Covalently Closed Circular DNA），作用是加入负超螺旋（Negative Supercoil）或松弛正超螺旋（Positive Supercoil）。旋转酶可以让DNA形成一个环状的结构（拓扑学上来说是一个正超螺旋的环环状的结构），通过切开一段DNA并让另一段DNA通过形成一个负超螺旋的环状结构。在这个过程中环绕数（Linking Number）减少了2（从正超螺旋Lk=＋1到负超螺旋Lk=－1,ΔLk=－2）。他的主要功用为纾解解旋酶解开DNA旋转时所造成的压力，因为解压缩旋转时会造成极大的逆旋转压。

DNA gyrase, also known as topoisomerase II or simply as gyrase, is an enzyme that relieves strain while double-stranded DNA is being unwound by helicase. This causes negative supercoiling of the DNA. The gyrase supercoils (or relaxes positive supercoils) into DNA by looping the template so as to form a crossing, then cutting one of the double helices and passing the other through it before releasing the break, changing the linking number by two in each enzymatic step. This process occurs in prokaryotes (in particular, in bacteria), whose single circular DNA is cut by DNA gyrase and the two ends are then twisted around each other to form supercoils. Gyrase has been found in the apicoplast of the malarial parasite Plasmodium falciparum, a unicellular eukaryote. Bacterial DNA gyrase is the target of many antibiotics, including nalidixic acid, novobiocin, and ciprofloxacin.