According to a new study from UCL and published in Nature, one of the basic building blocks of life, peptides, can be formed from the primitive precursors of amino acids under conditions as the same as those expected on the primordial Earth. The results of the study could be a missing piece of the puzzle of how life first formed.
Dr. Matthew Powner from UCL Chemistry, the lead author of the study, explained that peptides, which are chains of amino acids, are an essential element of all life on Earth. Peptides form the fabric of proteins, which serve as catalysts for biological process, but they require enzymes to control their formation from amino acids. So, how were the first enzymes made?
Dr. Powner and his team have demonstrated that the precursors to amino acids, called aminonitriles, can be quickly and selectively turned into peptides in water, taking advantage of their built-in reactivity with the help of other molecules that were present in the primordial environment.
Dr. Powner noted further that many researchers have sought to understand how peptides first formed to help life develop, however, nearly all of the research has focused on amino acids, so they overlooked the reactivity of their precursors. The precursors, aminonitriles, need harsh conditions, typically strongly acidic or alkaline, to form amino acids. And the amino acids must be recharged with energy to make peptides. The team discovered a way to bypass both of these steps, making peptides directly from energy-rich aminonitriles.
The researchers discovered that aminonitriles have the innate reactivity to achieve peptide bond formation in water with greater ease than amino acids. The researchers identified a sequence of simple reactions, combining hydrogen sulfide with aminonitriles and another chemical substrate ferricyanide, to yield peptides.
Pierre Canavelli, the first author of the study who completed it while at UCL, said that controlled synthesis, in response to environmental or internal stimuli, is a crucial element of metabolic regulation, so the team think that peptide synthesis could have been part of a natural cycle that took place in the early evolution of life.
The results of the study may also be useful to the field of synthetic chemistry, as amide bond formation is essential for many commercially critical synthetic materials, bioactive compounds, and pharmaceuticals. The technique used in this study is chemically unconventional but follows a pathway to ligate peptides that mimic biological process, unlike peptides-building pathways more commonly used in chemistry laboratories that run in the opposite direction and require expensive and wasteful reagents.