Aoyama H, Sato K, Fujii T, Fujimaki K, Inoue M, Mitsuhashi S
Episome Institute, Seta-gun, Japan.
Antimicrob Agents Chemother. 1988 Jan;32(1):104-9. doi: 10.1128/AAC.32.1.104.
DNA gyrase is a bacterial enzyme which catalyzes the ATP-dependent negative supercoiling of DNA. It is the accepted target of quinolones. The enzyme from Citrobacter freundii IID976 was purified by affinity chromatography on novobiocin-Sepharose and heparin-Sepharose. It had two subunits, designated A and B, which closely resembled those of the enzyme from Escherichia coli and Micrococcus luteus in enzymatic requirements. The inhibitory effects of the quinolones on the supercoiling activities of the enzyme correlated with their antibacterial activities. New quinolones were better inhibitors of DNA gyrase than nalidixic acid and pipemidic acid. We also purified DNA gyrase from a spontaneous nalidixic acid-resistant mutant (M2-5). The gyrases from IID976 and M2-5 were defined as mixtures of subunits As+Bs (s, susceptible) and Ar+Br (r, resistant), respectively. The supercoiling activities of reconstituted Ar+Br and Ar+Bs were more resistant to quinolones than As+Bs and As+Br. These findings indicate that one mechanism of C. freundii resistance against quinolones is resistance modification of the A subunit protein.
DNA促旋酶是一种细菌酶，可催化依赖ATP的DNA负超螺旋。它是喹诺酮类药物公认的作用靶点。通过在新生霉素-琼脂糖凝胶和肝素-琼脂糖凝胶上进行亲和层析，纯化了来自弗氏柠檬酸杆菌IID976的这种酶。它有两个亚基，分别命名为A和B，在酶促需求方面与来自大肠杆菌和藤黄微球菌的酶的亚基非常相似。喹诺酮类药物对该酶超螺旋活性的抑制作用与其抗菌活性相关。新型喹诺酮类药物比萘啶酸和吡哌酸是更好的DNA促旋酶抑制剂。我们还从自发耐萘啶酸突变体（M2-5）中纯化了DNA促旋酶。来自IID976和M2-5的促旋酶分别被定义为亚基As+Bs（s，敏感）和Ar+Br（r，耐药）的混合物。重组的Ar+Br和Ar+Bs的超螺旋活性比As+Bs和As+Br对喹诺酮类药物更具抗性。这些发现表明弗氏柠檬酸杆菌对喹诺酮类药物耐药的一种机制是A亚基蛋白的耐药性修饰。
