DAUNORUBICIN DPSH GENE ON CYCLIZATION PATTERN FOR TYPE II POLYKETIDE SYNTHASE

柔红霉素的早期中间体阿卡诺酸的生产 淡色链霉菌II型杂交菌生物合成柔红霉素 多聚体合成酶(PKS)基因作为序列的函数进行了研究 和在载体中克隆的基因类型，并从 ERME*发起人。与柔红霉素基因表达的比较 多酮合成酶(DPS)基因与其天然序列的正常顺序 启动子、dnrG单加氧酶、dpsA和dpsB酮还原酶和dpsF 当在变青链霉菌中按这个顺序克隆环化酶基因时， 产生了阿卡诺酸和SEK-43。后一种化合物是由 用乙酰辅酶A代替丙酰辅酶A作为发酵剂 并且不具有稠环芳香族体系的特性 阿卡诺酸。将DPSG替换为其TCMM同系物或 DnrG与灰链霉菌tcmJ PKS基因结合导致 极少或根本没有生产丙烯酸类。相比之下，添加了 Dpsh基因到tcmJ、dpsA、dpsB、tcmM、dpsE和dpsF基因盒 恢复了阿卡诺酸的环化模式。其原因是 Dpsh能够覆盖tcmM的负面影响并进行恢复 起动机和环化方式的选择都是正确的 未知，但总体结果表明，迭代类型II PKSS可以 功能异常，可能是蛋白质异常所致 化学计量或相互作用。目前，我们正在调查 表达这些基因盒时化合物的结构 其他变种人。

Production of aklanoic acid, an early intermediate of daunorubicin (dnr) biosynthesis in Streptomyces peucetius, by hybrid type II polyletide synthase (PKS) genes was studied as a function of the order and type of genes cloned in a plasmid vector and expressed from the ermE* promoter. Compared with expression of the daunorubicin polyketide synthase (dps) genes in the normal order from their native promoter, the dnrG monooxygenase, dpsA and dpsB ketoreductase and dpsF cyclase genes, when cloned in this order in Streptomyces lividans, produced aklanoic acid and SEK-43. The latter compound is made from acetyl-coenzyme A instead of propionyl-coenzyme A as the starter unit and does not have the characteristic fused ring aromatic system of aklanoic acid. Replacement of either dpsG with its tcmM homolog or dnrG with the Streptomyces glaucescens tcmJ PKS gene resulted in little or no aklanoic acid production. In contrast, addition of the dpsH gene to the tcmJ, dpsA, dpsB, tcmM, dpsE and dpsF gene cassette restored cyclization pattern of aklanoic acid. The reason for the ability of dpsH to override the negative effect of tcmM and restore both the proper choice of starter unit and cyclization pattern is unknown, but overall results indicate that iterative type II PKSs can function aberrantly, perhaps as a function of abnormal protein stoichiometries or interactions. Currently, we are investigating structures of compounds when these gene cassettes are expressed in other mutants.