The Biosynthesis of Monensin-A: Thymine, .BETA.-Aminoisobutyrate and Methacrylate Metabolism in Streptomyces cinnamonensis.
作者:DAVID O''HAGAN、SARAH V. ROGERS、GORDON R. DUFFIN、KEVIN A. REYNOLDS
DOI:10.7164/antibiotics.48.1280
日期:——
Feeding experiments with isotopically labelled samples of [13C, 2H3-methyl]-thymine, (R, S)-[1-13C]- and (R, S)-[13C-methyl]-β-aminoisobutyrates into monensin-A demonstrate that these metabolites can all contribute to the methylmalonyl-CoA pool in Streptomyces cinnamonensis, and implicate DNA catabolism as a contributory metabolic source of propionate carbon atoms for secondary metabolite biosynthesis. Further, these labelled compounds were unexpectedly incorporated into the butyrate unit of monensin-A, an observation which can be rationalised if β-aminoisobutyrate is converted to methacrylyl-CoA and then reduced to isobutyryl-CoA prior to conversion to butyryl-CoA by the action of isobutyryl-CoA mutase. Feeding experiments with [1-13C]- and [13C-methyl]-methacrylates and [3-13C]-isobutyrate suggest that these metabolites partition similarly between the butyrate and propionate units of monensin-A consistent with the view that isobutyryl-CoA and methacrylyl-CoA have a close metabolic relationship.
用同位素标记的[13C, 2H3-甲基]-胸腺嘧啶、(R, S)-[1-13C]-和(R, S)-[13C-甲基]-β-氨基丁酸盐样品喂养莫能菌素-A的实验表明,这些代谢物都能为肉桂链霉菌中的甲基丙二酰-CoA池做出贡献,并暗示DNA分解代谢是次生代谢物生物合成中丙酸碳原子的代谢来源。此外,这些标记化合物出乎意料地掺入了莫能菌素-A 的丁酸单元中,如果 β-氨基丁酸转化为甲基丙烯酰-CoA,然后在异丁烯酰-CoA 突变酶的作用下还原为异丁烯酰-CoA,再转化为丁酰-CoA,那么这一观察结果是合理的。用[1-13C]-和[13C-甲基]-甲基丙烯酸酯和[3-13C]-异丁酸进行的饲喂实验表明,这些代谢物在莫能菌素-A 的丁酸酯和丙酸酯单元之间的分配相似,这与异丁酰基-CoA 和甲基丙烯酰基-CoA 的代谢关系密切的观点一致。