BIOSYNTHESIS OF MAYTANSINOIDS AND ANALOGS

美坦辛(1)是一种非常有效的抗肿瘤药物，最初是通过 Kupchan和来自该工厂的同事Maytenus serrata(前M. 卵子)，在极低浓度(0.00002%)下出现 干重)。它的孤立只有凭借它的 非凡的生物效力，使用严格的生物测定指导 分馏法。1和一些同系物，主要是 酯侧链也是从该家族的其他植物中分离出来的 卫矛科，最高浓度(12毫克/千克干重)是 在疣腐病中发现。值得注意的是，梅坦辛类的成员 该家族，即阿斯米托菌素，随后被从 诺卡氏菌以及其他一些放线菌，提高了 质疑从植物材料中分离出来的化合物是否 由植物、共生微生物或污染微生物产生的。 后一种可能性由于隔离了 从几种苔藓植物中分离出的美丹素类化合物。尽管它具有非凡的威力 一种抗肿瘤药物，1，4，6-二氯苯酚作为抗癌药物的临床试验 由于剂量限制毒性，结果令人失望。结构-活性 研究，仅限于天然存在的化合物和 通过它们的半合成可以到达，并没有导致显著的 提高治愈率。然而，这些结构性的 变化必然主要限于C-3酯方面 链及其附着点周围区域；主干修饰 分子其他区域的官能团修饰有 由于无法接触到这些化合物，很大程度上仍未被勘探。 这为拟议的项目提供了最终的理由。在……下面 这个项目，PI将划定，在生化和在 遗传水平，微生物美坦素的生物合成， 阿司匹林。阿司匹林的全序列分析 生物合成的基因簇将为 携带和表达改变的突变生物的工程 添加了其中特定生物合成基因已被删除的簇 或者被来自其他生物合成途径的功能等价物取代。 这些将被分析用于生产天然的类似物 蛋黄素样结构。其次，微生物类美坦辛 生物合成基因及其序列将被用于分析DNA 1-产生植物和从它们分离出来的微生物 同源基因的存在，以鉴定真正的生物合成 从这些植物中分离出的梅坦辛素结构的起源。

Maytansine (1) is a very potent antitumor agent originally isolated by Kupchan and coworkers from the plant, Maytenus serrata (formerly M. ovatus), where it occurs in extremely low concentration (0.00002 percent of dry weight). Its isolation was only possible by virtue of its extraordinary biological potency, using a rigorous bioassay-guided fractionation. 1 and a number of congeners, mostly with variations in the ester side chain, were also isolated from other plants of the family Celastraceae, the highest concentration (12 mg/kg dry weight) being found in Putterlickia verrucosa. Notably, members of the maytansinoid family, the ansamitocins, were subsequently isolated from cultures of Nocardia species as well as some other Actinomycetes, raising the question whether the compounds isolated from the plant materials were produced by the plants or by symbiotic or contaminating microorganisms. The latter possibility was further reinforced by the isolation of maytansinoids from several mosses. Despite its extraordinary potency as an antitumor agent, clinical trials of 1 as an anticancer drug gave disappointing results due to dose limiting toxicity. Structure-activity studies, limited to the naturally occurring compounds and those accessible by semisynthesis from them, did not result in significant improvements of the therapeutic ratio. However, these structural variations were of necessity limited primarily to the C-3 ester side chain and the region around its attachment site; backbone modifications and functional group modifications in other regions of the molecule have remained largely unexplored due to inaccessibility of the compounds. This provides the ultimate rationale for the proposed project. Under this project, the PI will delineate, at the biochemical and at the genetic level, the biosynthesis of the microbial maytansinoids, the ansamitocins. The complete sequence analysis of the ansamitocins biosynthetic gene cluster will then lay the foundation for the engineering of mutant organisms harboring and expressing altered clusters in which specific biosynthetic genes have been deleted, added or replaced by functional equivalents from other biosynthetic pathways. These will be analyzed for the production of analogs of the natural maytansinoid structures. Secondly, the microbial maytansinoid biosynthesis genes and their sequences will be used to analyze the DNA of 1-producing plants and of microorganisms isolated form them for the presence of homologous genes in order to identify the true biosynthetic origin of the maytansinoid structures isolated from these plants.