Effects of Trimetaphosphate on Abiotic Formation and Hydrolysis of Peptides

Abstract

The primordial Earth probably had most of the factors needed for the emergence and development of life. It is believed that it had not only water, but also simple inorganic and organic materials. While studies since the 1950s on the origins of organic matter have established key roles for amino acids, conditions that would have promoted their condensation to make polymers, such as peptides or proteins, have yet to be fully defined. The condensation of amino acids in a water-rich environment is not thermodynamically favored. Therefore, the efficient formation of peptides requires the presence of a catalyst or the activation of a substrate. In living cells, the biosynthesis of proteins is assisted by enzymes and requires adenosine triphosphate (ATP), a relatively complex organic polyphosphate, which serves as an energy source. Outside the living organism, simpler inorganic polyphosphates can form active aminoacyl–phosphate anhydrides, which suggests the broader potential of phosphorus for enabling the polymerization of amino acids. However, this has yet to be demonstrated. To address this gap, aqueous solutions containing a simple dipeptide, diglycine, and a simple polyphosphate, trimetaphosphate, were dried, and reaction products were analyzed by high performance liquid chromatography and mass spectrometry (HPLC-MS). Different reaction environments, which were defined by the initial solution composition, pH, temperature, and incubation time, were found to affect the distribution and yield of products. Our results collectively provide strong evidence for reactions that both condense and hydrolyze peptides. It is noteworthy that the co-occurrence of reactions that form and cleave peptides are a central feature of Kauffman’s theory for the emergence of autocatalytic sets, which is a key step in the chemical origins of life.

Cyclic Dipeptides Formation From Linear Dipeptides Under Potentially Prebiotic Earth Conditions

“…Trimetaphosphate-induced linear peptide synthesis, amino acids in aqueous solutions, have been widely known for several decades ( Rabinowitz et al, 1969 ; Hill and Orgel, 2002 ; Sibilska et al, 2017 ). We aimed to discover whether P 3 m could promote the formation of cyclic dipeptides from cyclization of linear dipeptides under potentially prebiotic aqueous conditions.…”

Did Cyclic Metaphosphates Have a Role in the Origin of Life?

“…Condensed phosphates are capable of polymerizing amino acids under mild abiotic conditions (Sibilska et al 2017). A typical reaction mixture consisted of 200 mM diglycine solution and sodium trimetaphosphate adjusted to pH ~ 9.5 with NaOH.…”

“…These amines could be arginine and lysine, that are found in very high concentrations (ca. 90%) in acidocalcisomes (Rohloff et al 2003;284), and that can be polymerized by polyphosphates into peptides (Fondi et al 2007;Karki et al 2017;Kornberg 1995;Sibilska et al 2017).…”

Prebiotic Chemistry in Aqueous Environment: A Review of Peptide Synthesis and Its Relationship with Genetic Code

“…[ 21 ] Most experiments related to prebiotic peptide synthesis in the presence of cyclic or linear polyphosphates were performed at a neutral or slightly alkaline pH after Rabinowitz's important literature was published. [ 22‐29 ] The details of the reaction mechanism have been reported under alkaline aqueous solutions (Figure 1). [ 30 ] In general, the first amino acid reacts with P 3 m to form amino acid triphosphate (AAT), then AAT is hydrolyzed to pyrophosphates and cyclic acylphosphoramidates (CAPA); soon afterwards, the other amino acids attack CAPA to form phosphorylated dipeptides (phospho‐ AA 2 ); and then phospho‐AA 2 are hydrolyzed to inorganic phosphates and dipeptides (AA 2 ).…”