The antibiotic kijanimicin produced by the actinomycete Actinomadura kijaniata has a broad spectrum of bioactivities as well as a number of interesting biosynthetic features. To understand the molecular basis for its formation and to develop a combinatorial biosynthetic system for this class of compounds, a 107.6 kb segment of the A. kijaniata chromosome containing the kijanimicin biosynthetic locus was identified, cloned, and sequenced. The complete pathway for the formation of TDP-l-digitoxose, one of the two sugar donors used in construction of kijanimicin, was elucidated through biochemical analysis of four enzymes encoded in the gene cluster. Sequence analysis indicates that the aglycone kijanolide is formed by the combined action of a modular Type-I polyketide synthase, a conserved set of enzymes involved in formation, attachment, and intramolecular cyclization of a glycerate-derived three-carbon unit, which forms the core of the spirotetronate moiety. The genes involved in the biosynthesis of the unusual deoxysugar d-kijanose [2,3,4,6-tetradeoxy-4-(methylcarbamyl)-3-C-methyl-3-nitro-d-xylo-hexopyranose], including one encoding a flavoenzyme predicted to catalyze the formation of the nitro group, have also been identified. This work has implications for the biosynthesis of other spirotetronate antibiotics and nitrosugar-bearing natural products, as well as for future mechanistic and biosynthetic engineering efforts.

中文翻译：

---

Kijanimicin 基因簇的阐明：对螺环膦酸抗生素和硝基糖生物合成的洞察

由放线菌 Actinomadura kijaniata 产生的抗生素 kijanimicin 具有广泛的生物活性以及许多有趣的生物合成特征。为了了解其形成的分子基础并开发此类化合物的组合生物合成系统，鉴定、克隆和测序了含有 kijanimicin 生物合成位点的 A. kijaniata 染色体的 107.6 kb 片段。通过对基因簇中编码的四种酶的生化分析，阐明了形成 TDP-1-洋地黄毒苷（用于构建 kijanimicin 的两个糖供体之一）的完整途径。序列分析表明，苷元kijanolide 是由模块化I 型聚酮化合物合酶的联合作用形成的，这是一组参与形成、附着、甘油酸衍生的三碳单元的分子内环化，形成螺环膦酸盐部分的核心。参与不寻常脱氧糖 d-kijanose [2,3,4,6-tetradeoxy-4-(methylcarbamyl)-3-C-methyl-3-nitro-d-xylo-hexopyranose] 生物合成的基因，包括一种编码还鉴定了一种预计会催化硝基形成的黄素酶。这项工作对其他螺环膦酸盐抗生素和含亚硝基糖的天然产物的生物合成以及未来的机械和生物合成工程工作具有重要意义。6-tetradeoxy-4-(methylcarbamyl)-3-C-methyl-3-nitro-d-xylo-hexopyranose]，包括一种编码预测催化硝基形成的黄素酶的化合物，也已被鉴定。这项工作对其他螺环膦酸盐抗生素和含亚硝基糖的天然产物的生物合成以及未来的机械和生物合成工程工作具有重要意义。6-tetradeoxy-4-(methylcarbamyl)-3-C-methyl-3-nitro-d-xylo-hexopyranose]，包括一种编码预测催化硝基形成的黄素酶的化合物，也已被鉴定。这项工作对其他螺环膦酸盐抗生素和含亚硝基糖的天然产物的生物合成以及未来的机械和生物合成工程工作具有重要意义。