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Peptides can form without amino acids – ScienceDaily

Peptides, one of the fundamental building blocks of life, can be formed from primitive precursors of amino acids under conditions similar to those expected on Earth's primordial, according to a new study of the world. ; UCL.

The results, published in Nature, could be a missing piece of the life training puzzle.

"Peptides, which are amino acid chains, are an absolutely essential element of all life on Earth, they form the framework of proteins, which serve as catalysts for biological processes, but they themselves need 39 enzymes to control their formation from amino acids, "says lead author of the study, Dr. Matthew Powner (UCL Chemistry).

"So we had a classic problem with egg and chicken: how were the first enzymes made?"

He and his team have demonstrated that the precursors of amino acids, called aminonitriles, can be easily and selectively transformed into peptides in water, taking advantage of their own built-in responsiveness with the help of others. molecules present in primordial environments.

"Many researchers have sought to understand how peptides first formed to help life grow, but almost all research has focused on amino acids, so the reactivity of their precursors has been neglected, "said Dr. Powner.

Precursors, aminonitriles, require stringent conditions, generally strongly acidic or alkaline, to form amino acids. And then, amino acids must be recharged with energy to make peptides. The researchers found a way around these two steps by making peptides directly from energy-rich aminonitriles.

They discovered that aminonitriles have innate reactivity to allow the formation of peptide bonds in water more easily than amino acids. The team identified a sequence of simple reactions associating hydrogen sulphide with aminonitriles and another chemical substrate, ferricyanide, to give peptides.

"Controlled synthesis, in response to environmental or internal stimuli, is an essential element of metabolic regulation, so we believe that peptide synthesis could have been part of a natural cycle that occurred at all. beginning of the evolution of life, "said Pierre Canavelli, first author of the study that completed it at UCL.

The molecules that served as substrates to help form amide bonds in the experiments are degassed during volcanism and are probably all present on the early Earth.

"This is the first time that peptides are convincingly formed without using amino acids in water, using relatively mild conditions that may be available on early Earth," said the co-author. Dr. Saidul Islam (UCL Chemistry).

The results may also be useful in the field of synthetic chemistry, since the formation of amide bonds is essential for many synthetic materials, bioactive compounds and commercially important pharmaceuticals. The method used in this study is chemically unconventional but follows a pathway to bind (join) peptides that mimic biological processes, in contrast to the peptide construction pathways most commonly used in chemistry labs that operate in the opposite direction and require expensive and unnecessary reagents.

The research team is continuing their studies by looking for other pathways to peptides using aminonitriles and by examining the functional properties of the peptides produced by their experiments, in order to better understand how they could have helped to revive life 4 billion ago. years.

The research was funded by the Research Council of Engineering and Physical Sciences, the Simons Foundation and the Volkswagen Foundation.

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