Diversidad biosintética en S.diastáticus var. 108 y sus recombinantes genéticos Mejoras farmacológicas de antibióticos macrólidos polienos

Résumé

Nowadays, systemic fungal infection is considered to be an important problem to immunocompromised patients (antitumor drug applications, AIDS, organ transplantation, etc) and the threat increases due to limitation on antifungal agents available to fight mycoses. Amphotericin B is the preferred first-line drug for treatment of several systemic fungal infections, this polyene macrolide show good and broad antifungal activity; in addiction, is remarkable its low rate of resistant strains even after 50 years in clinical use. However its use is limited because the high toxicity derived from the low wather solubility and the interaction with cholesterol in mammalian membranes. Several attempts have been realized to solving this problem, construction of semisynthetic and genetically engineered derivates. These polyene macrolide have contributed to the current knowledge of the structure-activity relationships. It has been demonstrated that modification in the exocyclic carboxyl group of the macrolactone ring and/or the amino group of the mycosamine sugar of polyenes increase both antimicrobial activity and water solubility and low toxicity .Genetic manipulation is considerate a good way to generate new polyene macrolide with pharmacological improved properties. S. diastaticus var. 108 is a producer of the two polyenes, rimocidin and CE-108, the inactivation of the rimJ gene in S. diastaticus var. 108 increased yield of others closely related tetraenes: rimocidin D and CE-108D. The elucidation of the chemical structures of these compounds revealed the versatility of loading module, RimA, to choice so only acetyl CoA or butyryl CoA, but also propyonyl CoA as starter unit, and the 5 module to choice ethylmalonyl CoA and methylmalonyl CoA as elongation unit. The versatility of biosynthetic polyene pathway in S. diastaticus var.108 has been used in this work to analyze other loading modules, PimS0 and NysA, to choice one o more starter units. The activity of pcsA gene product, involve in a tailoring activity for the conversion ¿in vivo¿ the polyene macrolides in S.diastaticus var.108 is quite low in wile type strain. The rimJ disruption and amidotransferase carried mutant allowed the isolation of two new compounds: rimocidin E y CE-108 E which are amide derivate from rimocidin D y CE-108D respectively. This new amide compounds have showed improved pharmacological propertie,such as increase in the selective toxicity toward ergosterol-containing membranes. Finally, we could have seen that the low tetraene amides oproduction in S. diastaticus var. 108 is probably due to lack of synchronization between expression of rimA and pcsA genes