权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Studies on the Mechanism of Constructing Molecular Skeletons of Bioactive Polyether Metabolites

生物活性聚醚代谢物分子骨架构建机制研究

基本信息

批准号：
17208010
负责人：
OIKAWA Hideaki
金额：
$ 31.78万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17208010/
关键词：
polyethers biosynthesis polyketides cyclase epoxidase

项目摘要

Naturally occurring polyether metabolites show a broad range of biological activities and have been isolated from a number of organisms including soil bacteria (ionophore antibiotics), marine dinoflagelate (ladder polyether toxins), marine algae (triterpenes) and annonaceae plants (antitumor acetogenins). In the biosynthesis of polyether metabolites, it is proposed that a polyene precursor is stereoselectively epoxidized and then the subsequent sequential ring openings would afford polyether skeleton. This insightful hypothesis was supported by feeding experiments with isotopically labeled precursors in the biosynthesis of ionophore antibiotics. Recent genetic studies on monensin biosynththesis provided further supports for this hypothesis. Although enormous efforts to prove this hypothesis have been made, direct evidence on these enzymatic transformations has not been obtained. In this project, detailed biosynthetic studies on lasalocid A, an anticoccidium agent from Stretomyces lasaliensis, has carried out to elucidate the enzymatic construction of polyether skeleton.At first, we have succeeded identification of lasalocid biosynthetic gene cluster spanning 82 kb, and have also developed the stereocontroled synthesis of prelasalocid and its epoxide, which are plausible biosynthetic precursors of lasalocid. The most interesting feature in the polyether formation of lasalocid is an energetically disfavored 6-endo selective cyclization. Our efforts on enzymatic conversions of plausible biosynthetic precursors with the enzymes Lsd18 and Lsd19 overexpressed in Escherichia coli unambiguously showed that complex molecular skeleton of lasalocid is constructed by a sequencial ring opening of the corresponding epoxides with a single epoxide hydrolase Lsd19. This is the first example of the enzymatic formation of polyether skeleton.

天然存在的聚醚代谢物显示出广泛的生物活性，并且已经从许多生物体中分离出，包括土壤细菌（离子载体抗生素）、海洋甲藻（梯形聚醚毒素）、海藻（三萜）和番荔枝科植物（抗肿瘤乙酸配基）。在聚醚代谢物的生物合成中，提出了多烯前体立体选择性地环氧化，然后随后的顺序开环将提供聚醚骨架。这一有见地的假设得到了支持的喂养实验同位素标记的前体生物合成的离子载体抗生素。最近对莫能菌素生物降解的遗传学研究进一步支持了这一假说。虽然已经做出了巨大的努力来证明这一假设，但尚未获得关于这些酶促转化的直接证据。本项目对拉沙洛西（Stretomelasticlasaliensis）抗球虫药拉沙洛西A的生物合成进行了详细的研究，首先成功地鉴定了拉沙洛西生物合成基因簇，并建立了拉沙洛西前体化合物（prelasalocid）及其环氧化物的立体控制合成方法。拉沙洛西的聚醚形成中最有趣的特征是能量不利的6-内选择性环化。我们在大肠杆菌中过表达的酶Lsd 18和Lsd 19对可能的生物合成前体的酶促转化的努力明确地表明，拉沙洛昔的复杂分子骨架是通过用单个环氧化物水解酶Lsd 19对相应的环氧化物进行顺序开环而构建的。这是聚醚骨架酶促形成的第一个例子。