Detection and formation scenario of citric acid, pyruvic acid, and other possible metabolism precursors in carbonaceous meteorites
Detection and formation scenario of citric acid, pyruvic acid, and other possible metabolism precursors in carbonaceous meteorites
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DOI：
10.1073/pnas.1105715108
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发表时间：
2011-08-23
影响因子：
11.1
通讯作者：
Wang, Yi
中科院分区：
文献类型：
--
作者：
Cooper, George;Reed, Chris;Wang, Yi
碳质陨石向地球输送了各种有机化合物，这些化合物可能在生物化学途径的起源和/或进化中发挥了作用。一些看似古老而关键的代谢过程需要几种化合物，其中一些化合物相对不稳定，比如酮酸。因此，任何这种单个过程的益生菌环境都需要整个完整前体分子的连续远程来源和/或能量和紧凑的局部合成，特别是更脆弱的成员。到目前为止，丙酮酸、草酰乙酸、柠檬酸、异柠檬酸和异戊二酸等化合物(柠檬酸循环的所有成员)还没有在外星来源中被确定，或者作为一个组，作为一个组，作为在看似是益生菌条件下合成的一系列化合物的一部分。我们已经在碳质陨石和/或丙酮酸的低温(实验室)反应产物中确定了这些化合物和其他化合物。在陨石中，我们观察到许多是新报道的三类化合物的一部分：酮酸(丙酮酸及其同系物)、羟基三羧酸(柠檬酸及其同系物)和三羧酸。使用13C标记反应物的实验室合成表明，仅丙酮酸一种化合物就可以产生柠檬酸循环的几个(非酶)成员，包括草酰乙酸。一些陨石酮酸的同位素组成指向星际或太阳系前起源，表明这种化合物可能也存在于其他行星系统中。
Carbonaceous meteorites deliver a variety of organic compounds to Earth that may have played a role in the origin and/or evolution of biochemical pathways. Some apparently ancient and critical metabolic processes require several compounds, some of which are relatively labile such as keto acids. Therefore, a prebiotic setting for any such individual process would have required either a continuous distant source for the entire suite of intact precursor molecules and/ or an energetic and compact local synthesis, particularly of the more fragile members. To date, compounds such as pyruvic acid, oxaloacetic acid, citric acid, isocitric acid, and aketoglutaric acid (all members of the citric acid cycle) have not been identified in extraterrestrial sources or, as a group, as part of a " one pot" suite of compounds synthesized under plausibly prebiotic conditions. We have identified these compounds and others in carbonaceous meteorites and/ or as low temperature (laboratory) reaction products of pyruvic acid. In meteorites, we observe many as part of three newly reported classes of compounds: keto acids (pyruvic acid and homologs), hydroxy tricarboxylic acids (citric acid and homologs), and tricarboxylic acids. Laboratory syntheses using 13C-labeled reactants demonstrate that one compound alone, pyruvic acid, can produce several (nonenzymatic) members of the citric acid cycle including oxaloacetic acid. The isotopic composition of some of the meteoritic keto acids points to interstellar or presolar origins, indicating that such compounds might also exist in other planetary systems.