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  • Prebiotic synthesis of cysteine peptides that catalyze peptide ligation in neutral water.

Prebiotic synthesis of cysteine peptides that catalyze peptide ligation in neutral water.

Science (New York, N.Y.) (2020-11-14)
Callum S Foden, Saidul Islam, Christian Fernández-García, Leonardo Maugeri, Tom D Sheppard, Matthew W Powner
ABSTRACT

Peptide biosynthesis is performed by ribosomes and several other classes of enzymes, but a simple chemical synthesis may have created the first peptides at the origins of life. α-Aminonitriles-prebiotic α-amino acid precursors-are generally produced by Strecker reactions. However, cysteine's aminothiol is incompatible with nitriles. Consequently, cysteine nitrile is not stable, and cysteine has been proposed to be a product of evolution, not prebiotic chemistry. We now report a high-yielding, prebiotic synthesis of cysteine peptides. Our biomimetic pathway converts serine to cysteine by nitrile-activated dehydroalanine synthesis. We also demonstrate that N-acylcysteines catalyze peptide ligation, directly coupling kinetically stable-but energy-rich-α-amidonitriles to proteinogenic amines. This rare example of selective and efficient organocatalysis in water implicates cysteine as both catalyst and precursor in prebiotic peptide synthesis.

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Sodium sulfide