Power Patrick, Dunne Terence, Murphy Barry, Nic Lochlainn Laura, Rai Dilip, Borissow Charles, Rawlings Bernard, Caffrey Patrick
School of Biomolecular and Biomedical Science and Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
Chem Biol. 2008 Jan;15(1):78-86. doi: 10.1016/j.chembiol.2007.11.008.
Site-directed mutagenesis and gene replacement were used to inactivate two ketoreductase (KR) domains within the amphotericin polyketide synthase in Streptomyces nodosus. The KR12 domain was inactivated in the DeltaamphNM strain, which produces 16-descarboxyl-16-methyl-amphotericins. The resulting mutant produced low levels of the expected 15-deoxy-15-oxo analogs that retained antifungal activity. These compounds can be useful for further chemical modification. Inactivation of the KR16 domain in the wild-type strain led to production of 7-oxo-amphotericin A and 7-oxo-amphotericin B in good yield. 7-oxo-amphotericin B was isolated, purified, and characterized as the N-acetyl methyl ester derivative. 7-oxo-amphotericin B had good antifungal activity and was less hemolytic than amphotericin B. These results indicate that modification at the C-7 position can improve the therapeutic index of amphotericin B.
利用定点诱变和基因置换技术使诺卡氏链霉菌中两性霉素聚酮合酶内的两个酮还原酶（KR）结构域失活。在产生16-脱羧基-16-甲基两性霉素的DeltaamphNM菌株中，KR12结构域被失活。所得突变体产生低水平的保留抗真菌活性的预期15-脱氧-15-氧代类似物。这些化合物可用于进一步的化学修饰。在野生型菌株中KR16结构域的失活导致高产率产生7-氧代两性霉素A和7-氧代两性霉素B。分离、纯化了7-氧代两性霉素B，并将其表征为N-乙酰甲酯衍生物。7-氧代两性霉素B具有良好的抗真菌活性，并且比两性霉素B的溶血作用小。这些结果表明在C-7位进行修饰可以提高两性霉素B的治疗指数。
