BIOSYNTHESIS AND METABOLISM OF CYCLOPENTANOIDS

环戊类化合物的生物合成和代谢

• 批准号: 6179175
• 负责人: RONALD J PARRY
• 金额: $ 19.16万
• 依托单位: RICE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-09-01 至 2002-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6179175
• 关键词: Pseudomonas; Streptomyces; antineoplastic antibiotics; biosynthesis; chemical structure; enzyme mechanism; enzyme substrate; esterase; microorganism metabolism; nucleoside analog; oxygenases; plant poisons; purine /pyrimidine metabolism

DESCRIPTION: Investigations of two novel cyclopentanoid natural products will be continued. The first is the antibiotic aristeromycin, a cyclopentyl analog of adenosine produced by Streptomyces citricolor, along with the cyclopentenyl adenosine analog neplanocin A, which is an antitumor and antiviral agent. Previous investigations of aristeromycin biosynthesis established that the cyclopentane ring is generated by C-C bond formation between C-2 and C-6 of glucose, and provided evidence that carbocyclic analogs of the "normal" purine biosynthetic pathway may be intermediates. Also, a novel enzyme that catalyzes the anti-Markovinikov reduction of neplanocin A to aristeromycin was isolated and partially purified from S. citricolor. Future studies will focus on furthe purification of this enzyme, cloning of the gene coding for the enzyme, overexpression of the enzyme, and elucidation of the mechanism of the reductio process. Two unsaturated carbocyclic PRPP analogs that may be intermediates in aristeromycin biosynthesis will also be synthesized and evaluated using cell-free extracts of S. citricolor. The second cyclopentanoid to be investigated is the phytotoxin coronatine, produced by Pseudomonas syringae. The cyclopropyl amino acid moiety of the toxin, coronamic acid, has been found to be biosynthesized from L-alloisoleucine by a highly unusual process that proceeds with retention of the nitrogen atom of the amino acid and the loss of only two hydrogen atoms, one from the alpha-position of the amino acid and one from the methyl group. Future investigations will examine the details of coronamic acid biosynthesis and will be carried out in collaboration with Dr. Bender of Oklahoma State University who has sequenced three genes involved in coronamic acid biosynthesis. The two genes whose role appears clear will be overexpressed and their biochemistry studied. The product of the first gene (CmaA) appears to activate L-alloisoleucine as an acyl adenylate, convert it t an enzyme bound thiol ester, and then clize it to enzyme-bound coronamic acid. A motif in CmaA suggests it is likely to be an iron-dependent dioxygenase. The product of the second gene (CmaT) appears to be a thioesterase whose role is t release coronamic acid from CmaA. Mechanistic studies with both of these enzymes are proposed. The potential use of the CmaA gene for construction of hybrid peptide antibiotics containing L-alloisoleucine or coronamic acid will also be explored, using surfactin biosynthesis in B. subtilis as a model system.

描述：两种新型环戊素天然产品的研究 将继续。 首先是抗生素瘤霉素，一种环戊烯 由淀粉菌柠檬色产生的腺苷的类似物以及 环戊烯基腺苷类似物中的内皮素A，是抗肿瘤， 抗病毒剂。 先前对瘤霉素生物合成的研究 确定环戊烷环是通过C-C键形成产生的 在葡萄糖的C-2和C-6之间，并提供了证据表明碳环糖 “正常”嘌呤生物合成途径的类似物可能是中间体。 另外，一种新型酶，可催化抗马科维尼科夫的减少 分离NedranocinA至瘤霉素，并从S.部分纯化。 柠檬色。 未来的研究将重点放在净化这一点上 酶，编码酶的基因的克隆，过表达的过表达 酶，并阐明还原过程的机理。 二 可能是中间体的不饱和碳环类似物类似物 瘤霉素的生物合成也将通过使用 柠檬色链球菌的无细胞提取物。 第二个环戊酸是 研究的是植物毒素冠状动脉素，由丁香假单胞菌产生。 毒素冠状酸的环丙基氨基酸部分已经是 发现通过高度不寻常的过程从L- Alloisolecine中生物合成 继续进行氨基酸的氮原子和 仅损失两个氢原子，一个来自氨基的α-位置 酸，一个来自甲基。 未来的调查将检查 冠状酸生物合成的细节，将在 与已测序的俄克拉荷马州立大学本德尔博士合作 参与冠状酸生物合成的三个基因。 两个基因的基因 角色显然会过表达，并研究了其生物化学。 第一个基因（CMAA）的乘积似乎激活L-异亮氨酸盐作为 酰基腺苷酸，将其转换为酶结合的硫醇酯，然后将其粘合 它可以结合酶结合的冠状酸。 CMAA中的一个主题表明它很可能 成为铁依赖性二氧酶。 第二基因（CMAT）的乘积 似乎是一种硫酯酶，其作用是t释放冠状酸 CMAA。 提出了这两种酶的机械研究。 这 CMAA基因的潜在用途用于构建杂交肽 含有L-抗甲甲酸酯或冠状酸的抗生素也将是 探索，使用枯草芽孢杆菌中的表面生物合成作为模型系统。