講演情報
[U17-P01]Experimental study on the recycling of glycolaldehyde through oxidation reaction in prebiotically plausible conditions
*浅倉 裕太1、藏 暁鳳1、上野 雄一郎1,2,3 (1.東京科学大学、2.東京科学大学地球生命研究所、3.海洋研究開発機構)
キーワード：
CO大気、生成物の酸化サイクル、前駆代謝仮説
In order to understand origin of life, it is essential to consider how organic compounds are produced in planetary environments and sustained as a persistent chemical system under plausible early Earth conditions. Our recent studies have demonstrated that small aldehydes, not only formaldehyde but also acetaldehyde, glyoxal and glycolaldehyde were supplied continuously through photochemistry of CO2/CO/H2O atmospheres [1], [2]. Among these, glycolaldehyde and acetaldehyde are known to undergo aldol reaction, as well as oxidized by co-generated oxidant (OH, HO2, and H2O2), yielding a wide variety of carbohydrates and carboxylic acids, some of which consist a persistent cyclic reaction network (the Primitive Respiration Cycle: PRC) and could be a blue print of biological metabolism[2]. In this study, we report more detailed study to clarify how the glycolaldehyde is recycled through the PRC and how the chemical system could be sustained in and adapted to the environment. A simple oxidation experiment of glycerate, an intermediate of the PRC, by hydrogen peroxide as an oxidant clearly demonstrated that glycolaldehyde was generated by the oxidation of glycerate probably through decarboxylation of tartronate semialdehyde (TSA), which is one of the oxidation products of glycerate. Another oxidation product of glycerate is hydroxypyruvate, which was further oxidized into glycolate, glyoxylate, formate and then finally CO2. Therefore, at least half of the glycolaldehyde can be reproduced if excess formaldehyde is available, where aldol addition of glycolaldehyde generates glyceraldehyde, which is subsequently oxidized to reform glycerate. We will further study the reaction network by considering all the other side reactions, estimate the rate constant for each reaction depending on pH or other factors, and predict the time evolution of these compound concentrations. Based on the estimated kinetic parameters, we will assess the bottlenecks of the cycle, and identify the key environmental factors required to sustain the reaction cycle.
[1] Zang X., Ueno Y., and Kitadai N. (2022) Photochemical Synthesis of Ammonia and Amino Acids from Nitrous Oxide. Astrobiology, 22: 387-398.
[2] Ueno Y., Zang X., Asakura Y., Fong A., Kawade W., Isoda K., Yokoyama T., Kitadai N. (in review) Atmospheric UV synthesis of aldehydes and oxidant from CO2, CO and H2O initiating the first ancestral metabolism. PEPS.
[1] Zang X., Ueno Y., and Kitadai N. (2022) Photochemical Synthesis of Ammonia and Amino Acids from Nitrous Oxide. Astrobiology, 22: 387-398.
[2] Ueno Y., Zang X., Asakura Y., Fong A., Kawade W., Isoda K., Yokoyama T., Kitadai N. (in review) Atmospheric UV synthesis of aldehydes and oxidant from CO2, CO and H2O initiating the first ancestral metabolism. PEPS.