Department of Chemistry, Rikkyo University, Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan.
Department of Chemistry and Life Science, Graduate School of Engineering Science, Yokohama National University, Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
Molecules. 2024 Sep 16;29(18):4403. doi: 10.3390/molecules29184403.
It is not known why the number of proteinogenic amino acids is limited to 20. Since Miller's experiment, many studies have shown that amino acids could have been generated under prebiotic conditions. However, the amino acid compositions obtained from simulated experiments and exogenous origins are different from those of life. We hypothesized that some simple precursor compounds generated by high-energy reactions were selectively combined by organic reactions to afford a limited number of amino acids. To this direction, we propose two scenarios. One is the reaction of HCN with each side-chain precursor (the aminomalononitrile scenario), and the other is alkylation of the "complex glycine precursor", which is the main product of proton irradiation of the primordial atmosphere (the new polyglycine scenario). Here, selective formation of the 20 amino acids is described focusing on the latter scenario. The structural features of proteinogenic amino acids can be described systematically. The scenario consists of three stages: a high-energy reaction stage (Gly, Ala, Asn, and Asp were established); an alkylation stage (Gln, Glu, Ser, Thr, Val, Ile, Leu, and Pro were generated in considerable amounts); and a peptide formation stage (Phe, Tyr, Trp, His, Lys, Arg, Cys, and Met were selected due to their structural advantages). This scenario is a part of the evolution of Garakuta World, in which many prebiotic materials are contained.
目前尚不清楚为什么蛋白质氨基酸的数量被限制在 20 种。自米勒实验以来，许多研究表明，在原始生命形成之前氨基酸可能已经产生。然而，从模拟实验和外源获得的氨基酸组成与生命的不同。我们假设一些简单的前体化合物通过高能反应生成，然后通过有机反应选择性地结合，从而产生有限数量的氨基酸。为此，我们提出了两种情景。一种是 HCN 与每个侧链前体反应（氨甲丙二腈情景），另一种是“复杂甘氨酸前体”的烷基化，它是原始大气质子辐照的主要产物（新的多甘氨酸情景）。在这里，我们重点关注后一种情景，描述了 20 种蛋白质氨基酸的选择性形成。蛋白质氨基酸的结构特征可以系统地描述。该情景包括三个阶段：高能反应阶段（形成 Gly、Ala、Asn 和 Asp）；烷基化阶段（大量生成 Gln、Glu、Ser、Thr、Val、Ile、Leu 和 Pro）；以及肽形成阶段（由于其结构优势，选择了 Phe、Tyr、Trp、His、Lys、Arg、Cys 和 Met）。这个情景是 Garakuta 世界进化的一部分，其中包含了许多原始生命材料。
