BIO-ENGINEERING OF COMPOUNDS ACTIVE AGAINST MDR CANCER

描述：Nonactin是170-kDa-P-糖蛋白的抑制剂 4 ′-O-四氢吡喃阿霉素介导的多药耐药细胞外排 K562细胞。 Nonactin及其macrotetrolide同系物 als在体外对癌细胞系有活性， 在小鼠体内研究中的活性。 此外，大环内酯类用作 典型的离子载体抗生素对革兰氏阳性细菌，真菌， 和分枝杆菌。 Nonactin不是目前的候选药物，因为它 毒性相对较高。 然而，天然存在的同系物具有 更大的活动比nonactin：从QSAR分析，我们提出了一系列的 这些化合物具有潜在的高得多的活性。 大环内酯同系物的化学合成并不简单，因为它 需要分别合成九乳酸的两种对映体; 将九乳酸单元选择性地转化为四聚体中间体;以及 最后进行大环内酯化反应形成大环四内酯环。 相比之下，灰色链霉菌菌株ETH A7796可以很容易地将 1 gL-1的nonactin的发酵。 我们建议将最好的方面联合收割机 化学合成和“生物合成”来制造新的macrotetrolides。 化学合成将用于制备外消旋九乳酸类似物， 建立高效的路线。 基因改变的“生物合成” 链球菌菌株griseus将实现立体特异性生物转化 将九乳酸类似物转化为新的大环内酯。 这项建议的具体目标是： 1. 从S. griseus ETH A7796中的关键酶， 非肌动蛋白生物合成，非乳酸合酶，催化 一种非环状的前体，可以转化为九乳酸。 2. 目的分离和鉴定非肌动蛋白生物合成簇基因。 3. 使用突变株，在nonactin生物合成中被破坏， 原型macrotetrolide类似物，并研究其物理和 生物学特性

DESCRIPTION: Nonactin is an inhibitor of the 170-kDa-P-glycoprotein mediated efflux of 4'-O-tetrahydropyranyladriamycin in multi-drug resistant erythroleukemia K562 cells. Nonactin and its macrotetrolide homologues are als active against cancer cell lines in vitro and have shown tumor reducing activity in in vivo studies with mice. Further, the macrotetrolides act as typical ionophore antibiotics being effective against Gram+ bacteria, fungi, and mycobacteria. Nonactin is not a current drug candidate because of its relatively high toxicity. The naturally occurring homologues, however, have greater activity than nonactin: from a QSAR analysis we propose a series of ne compounds which have potentially much higher activity. Chemical synthesis of macrotetrolide homologues is not trivial as it requires the separate synthesis of both enantiomers of nonactic acid; selective assembl of nonactic acid units into a tetrameric intermediate; and finally a macrolactonization reaction to form the macrotetrolide ring. Streptomyces griseus strain ETH A7796, in comparison, can readily make over 1 gL-1 of nonactin in fermentation. We propose to combine the best aspects of chemical synthesis and 'biosynthesis' to make new macrotetrolides. Chemical synthesis will be used to make racemic nonactic acid analogs via established, efficient routes. 'Biosynthesis' in a genetically altered strain of S. griseus will achieve the stereospecific biotransformation of the nonactic acid analogs into new macrotetrolides. The specific aims of this proposal are: 1. To purify from S. griseus ETH A7796 and characterize the key enzyme in nonactin biosynthesis, nonactate synthase, which catalyzes the conversion of a acyclic precursor into nonactic acid. 2. To isolate and characterize genes of the nonactin biosynthesis cluster. 3. To use a mutant strain, disrupted in nonactin biosynthesis, to make four prototypical macrotetrolide analogs, and to study their physical and biologica properties.