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This theoretical paper proposes that homochirality in peptides (the exclusive use of one mirror-image form of amino acids) represents the first critical milestone in the origin of life, occurring approximately 4 billion years ago in Earth's crust under conditions of reduced water activity. The authors argue that homochiral peptides are inherently unstable in the cytosol of living organisms, gradually losing their chirality over time through incorporation of D-amino acids, which contributes to organismal aging and mortality. They suggest that metabolism and genetic systems evolved in an environment already containing homochiral peptides, with cellular life later emerging at hot spring interfaces between the crust and ancient ocean.
Why it matters
This work attempts to establish a chronological order for key evolutionary events at life's origin and links peptide instability to fundamental questions about aging and mortality. If validated, this framework could inform our understanding of why life uses exclusively L-amino acids and provide insights into the chemical constraints that shaped early biochemistry.
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Abstract: Living organisms have some common structures, chemical reactions, and molecular structures.
The organisms consist of cells with cell division; they have homochirality of protein and carbohydrate units, metabolism, and genetics, and they are mortal. The molecular structures and chemical reactions underlying these features are common to all, from the simplest bacteria to human beings. The origin of life is evolutionary, with the emergence of a network of spontaneous biochemical reactions, and evolution has taken place over a very long time.
The evolution contains, however, some “landmarks” and bottlenecks, which in a revolutionary manner directed the evolution, and the article establishes an order of some of these events. Recent articles show that peptides in living organisms are long-time unstable, with loss of their secondary homochiral conformations and with D-amino acids. Based on these observations and an extensive scientific literature on Abiogenesis, we argue that the first milestone in the prebiotic evolution is at the emergence of homochiral peptides in an aqueous solution with a high concentration of amino acids and a lower water activity than in the cytosol in living organisms. The homochiral peptides in cytosol are unstable, and the long-time aging of peptides in the cytosol causes mortality of living organisms. The metabolism and genetics are established in an environment with homochiral peptides in the Earth’s crust for $approx$ 4 Gyr ago at a lower water activity than in the cytosol in living organisms.
Finally, the cells with cell division are established in the Hot Springs environment at the interface between the crust and the Hadean Ocean.
Source: Origin of homochirality in peptides: The first milestone at the origin of life