Engineered biosynthesis of regioselectively modified aromatic polyketides using bimodular polyketide synthases.
Engineered biosynthesis of regioselectively modified aromatic polyketides using bimodular polyketide synthases.
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DOI：
10.1371/journal.pbio.0020031
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发表时间：
2004-02
期刊：
影响因子：
9.8
通讯作者：
Khosla C
中科院分区：
文献类型：
--
作者：
Tang Y;Lee TS;Khosla C
细菌芳香族聚酮，如四环素和阿霉素，是一类重要的天然产物，由放线菌产生的次生代谢物。它们的骨架是由聚酮合成酶(PKS)从丙二酰辅酶A单位衍生而来的。新生的聚酮链是由最小的PKS合成的，PKS是一个由四个解离的酶组成的模块。虽然大多数芳香族聚酮骨架的生物合成是通过丙二酸基构建块的脱羧基(导致乙酸基)启动的，但一些聚酮类化合物，如雌激素受体拮抗剂R1128，是由非乙酸酯引物衍生而来的。了解非醋酸酯引发的机制可以导致具有改善药理性质的新型聚酮的生物合成。最近的生化分析表明，非乙酸酯启动是两个分离的具有正交分子识别特征的PKS模块逐步激活的结果。在这些PKS中，除了最小PKS模块之外，还存在合成起始器单元的启动模块。在这里，我们描述了一种工程生物合成区域选择性修饰的芳香族聚酮的一般方法。当与R1128起始模块共表达时，放线菌素最小PKS产生了带有丙酰基和异丁酰基单元的新型六酮化合物。将四环素最小PKS与R1128起始模块结合，可合成类似的八肽类化合物。酮还原酶和环化酶等剪裁酶能有效地处理非天然多酮类物质。基于这些发现，杂化PKSS被设计成合成具有可预测的官能团修饰的新的蒽醌抗生素。我们的结果表明：(I)双模芳香族PKS呈现了一个用非醋酸酯前体引发芳香族聚酮骨架的一般机制；(Ii)最小PKS通过计算结合到骨架中的原子的数量而不是延伸循环的数量来控制聚酮链的长度；以及(Iii)相反，辅助的PKS酶，如酮还原酶、芳香化酶和环酶，识别主链中的特定官能团，而不是总的链长。在这项研究中设计的蒽环类药物中，有一些化合物具有(I)比R1128更好的抗乳腺癌细胞株MCF-7的活性，以及(Ii)对葡萄糖-6-磷酸转移酶的抑制活性，这是治疗II型糖尿病的一个有吸引力的靶点。微生物次级代谢产物的类似物，包括许多抗生素和抗肿瘤药物，可以从聚酮主干的不寻常的引子单元中进行工程，以创造具有前景的新的药理特性的新的药物化合物。
Bacterial aromatic polyketides such as tetracycline and doxorubicin are a medicinally important class of natural products produced as secondary metabolites by actinomyces bacteria. Their backbones are derived from malonyl-CoA units by polyketide synthases (PKSs). The nascent polyketide chain is synthesized by the minimal PKS, a module consisting of four dissociated enzymes. Although the biosynthesis of most aromatic polyketide backbones is initiated through decarboxylation of a malonyl building block (which results in an acetate group), some polyketides, such as the estrogen receptor antagonist R1128, are derived from nonacetate primers. Understanding the mechanism of nonacetate priming can lead to biosynthesis of novel polyketides that have improved pharmacological properties. Recent biochemical analysis has shown that nonacetate priming is the result of stepwise activity of two dissociated PKS modules with orthogonal molecular recognition features. In these PKSs, an initiation module that synthesizes a starter unit is present in addition to the minimal PKS module. Here we describe a general method for the engineered biosynthesis of regioselectively modified aromatic polyketides. When coexpressed with the R1128 initiation module, the actinorhodin minimal PKS produced novel hexaketides with propionyl and isobutyryl primer units. Analogous octaketides could be synthesized by combining the tetracenomycin minimal PKS with the R1128 initiation module. Tailoring enzymes such as ketoreductases and cyclases were able to process the unnatural polyketides efficiently. Based upon these findings, hybrid PKSs were engineered to synthesize new anthraquinone antibiotics with predictable functional group modifications. Our results demonstrate that (i) bimodular aromatic PKSs present a general mechanism for priming aromatic polyketide backbones with nonacetate precursors; (ii) the minimal PKS controls polyketide chain length by counting the number of atoms incorporated into the backbone rather than the number of elongation cycles; and (iii) in contrast, auxiliary PKS enzymes such as ketoreductases, aromatases, and cyclases recognize specific functional groups in the backbone rather than overall chain length. Among the anthracyclines engineered in this study were compounds with (i) more superior activity than R1128 against the breast cancer cell line MCF-7 and (ii) inhibitory activity against glucose-6-phosphate translocase, an attractive target for the treatment of Type II diabetes. Analogues of microbial secondary metabolites, which include many antibiotics and antitumor drugs, can be engineered from unusual primer units of the polyketide backbone to create new medicinal compounds with promising novel pharmacological properties
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影响因子：
3.5
作者：
BIBB, MJ;SHERMAN, DH;HOPWOOD, DA
通讯作者：
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