质粒携带与磺胺耐药有关的因子,早已为人们所共知。然而,只是近来人们才研究其生化机理,Wise和Abou—Donia的工作,证实了从临床分离得到的R质粒,由其密码能合成一种耐药的双氢蝶脂合成酶。作者在实验中也分别获得类似的结果。由染色体密码合成的双氢蝶脂合成酶,早已证明能使磺胺作为底物,形成稳定的含磺胺的双氢蝶脂类物,从而使磺胺降低药效。质粒传递密码合成的酶,似乎和耐药性变异的细菌染色体密码合成的酶大不相同,前者有很高的 Plasmids carrying sulfa drug resistance-related factors, has long been known. However, it has only recently been studied biochemically. The work of Wise and Abou-Donia confirmed the isolation of the clinically isolated R plasmid from which a drug-resistant dihydrotestosterone synthase could be synthesized. The authors also obtained similar results in experiments. Dihydrotestosterone synthase, which is synthesized from the chromosomal code, has long been shown to make sulfa as a substrate to form a stable sulindamine-containing dihydrogdene lipid that will reduce its efficacy. Enzymes that pass on to the plasmid-delivered codons appear to be quite different from enzymes synthesized by the bacterial chromosomal code that mutate in resistance, with the former having a high