BIOSYNTHESIS OF MAYTANSINOIDS AND ANALOGS

美登素及其类似物的生物合成

• 批准号: 6329018
• 负责人: HEINZ G FLOSS
• 金额: $ 22.9万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-01-15 至 2002-07-21
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6329018
• 关键词: Streptomyces; bacterial genetics; biosynthesis; biotechnology; carbohydrate analog; drug design /synthesis /production; drug screening /evaluation; enzyme activity; microorganism metabolism; nucleic acid sequence; open reading frames; plant extracts; recombinant proteins; tissue /cell culture

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.

美登素（1）是一种非常有效的抗肿瘤剂，最初由 Kupchan和来自该工厂的同事，锯叶美登木（原M。 卵形），在那里它以极低的浓度（0.00002%）出现 干重）。 它的孤立是唯一可能的凭借其 非凡的生物效力，使用严格的生物测定指导， 分馏 1和许多同类物，大多数都有变化 酯侧链，也从该科的其它植物中分离得到 卫矛科，最高浓度（12毫克/千克干重）为 Putterlickia verrucosa中发现。 值得注意的是，美登木素生物碱的成员 家族，安丝菌素，随后从培养物中分离出来， 诺卡氏菌属以及其他一些放线菌，提高了 从植物材料中分离出的化合物是否 由植物或由共生或污染微生物产生。 后一种可能性因孤立 几种苔藓中的美登木素生物碱。尽管它具有非凡的效力， 一种抗肿瘤剂，1作为抗癌药的临床试验给出了 由于剂量限制毒性，结果令人失望。 构效 研究，仅限于天然存在的化合物和那些 从他们的半合成，并没有导致显着的 提高治疗率。 然而，这些结构 变化必然主要限于C-3酯侧 链及其连接位点周围的区域;骨架修饰 并且在分子的其它区域中的官能团修饰具有 由于无法进入这些化合物，这些化合物大部分尚未勘探。 这是拟议项目的最终理由。 下 在这个项目中，PI将描述生物化学和 遗传水平，微生物美登木素的生物合成， 安丝菌素安丝菌素的全序列分析 生物合成基因簇将为生物合成奠定基础。 携带和表达改变的 其中特定的生物合成基因已被删除的集群， 或被来自其它生物合成途径的功能等同物替代。 这些将被分析用于生产天然的类似物。 美登木素结构 其次，微生物美登木素 生物合成基因及其序列将用于分析DNA 1-生产的植物和微生物分离出他们的 同源基因的存在，以确定真正的生物合成 从这些植物中分离的美登木素结构的起源。