PPtase高表达菌株Streptomyces ghanaensis的发酵及其产物cytoxazone的发现

Fermentation analysis of the PPtase overexpressed Streptomyces ghanaensis strain and the identification of cytoxazone

天然产物是新药发现的重要源泉。然而,由于大多数天然产物的生物合成途径在实验室培养的情况下处于沉默状态,因此需要对其生物合成调控环节进行干预,从而使微生物激活其自身的生物合成。在前期工作中,本研究发展了一种高效激活沉默天然产物的方法。通过在微生物体内过表达磷酸泛酰巯基乙胺基转移酶(phosphopantetheinyl transferase,PPtase),可以高效激活一系列沉默天然产物的生物合成。基于该工作基础,本研究从一株PPTase过表达的嘎纳链霉菌Streptomyces ghanaensis CGMCC4.1967中,发现了一个新的激活天然产物。经分离后通过结构鉴定该产物为Th2细胞Ⅱ型细胞因子细胞特异性抑制剂cytoxazone。Cytoxazone此前是在一株分离自广岛的链霉菌(S/reptomyces sp.)的发酵液中发现,其在嘎纳链霉菌中为首次发现。本研究的结果证实了S.ghanaensis CGMCC4.1967可以产生cytoxazone。这部分工作将对阐明此类重要天然产物的生物合成机制,并对其进行合成生物学改造以获得更好活性的细胞因子抑制剂建立基础。

Natural products are critical for drug discovery and development.However,this endeavor is often challenged by the wide inactivation or silence of natural products biosynthetic pathways.We recently developed a highly efficient approach to activate cryptic/silenced biosynthetic pathways through overexpression of thephosphopantetheinyl transferase(PPtase)in vivo.Based on these studies,we herein identified a novel activated metabolite-cytoxazone from the Streptomyces ghanaensis CGMCC 4.1967 PPtase overexpressing strain.Cytoxazone was previously discovered from Streptomyces sp.and has a potent inhibitory activity against Th2 cells to produce type II cytokines.Its production in Streptomyces ghanaensis CGMCC 4.1967 was not known before and our results confirmed that the Streptomyces ghanaensis CGMCC 4.1967 indeed had the capability to produce this secondary metabolite.Moreover,the successful activation of cytoxazone production demonstrated the effectiveness of PPtasebased approach.This result provided a solid basis for further elucidation of its biosynthesis and generation of structural diversity through pathway engineering.