A prebiotic Krebs cycle analog generates amino acids with H2 and NH3 over nickel
Harpreet Kaur, Sophia A. Rauscher, Emilie Werner, Youngdong Song, Jing Yi, Wahnyalo Kazöne, William Martin, Harun Tüysüz, Joseph Moran
Abstract
Hydrogen (H 2 ) has powered microbial metabolism for roughly 4 billion years. The recent discovery that it also fuels geochemical analogs of the most ancient biological carbon fixation pathway sheds light on the origin of metabolism. However, it remains unclear whether H 2 can sustain more complex nonenzymatic reaction networks. Here, we show that H 2 drives the nonenzymatic reductive amination of six biological ketoacids and glyoxylate to give the corresponding amino acids in good yields using ammonium concentrations ranging from 6 to 150 mM. Catalytic amounts of nickel or ground meteorites enable these reactions at 22°C and pH 8. The same conditions promote an H 2 -dependent ketoacid-forming reductive aldol chemistry that co-occurs with reductive amination, producing a continuous reaction network resembling amino acid synthesis in the metabolic core of ancient microbes. The results support the hypothesis that the earliest biochemical networks could have emerged without enzymes or RNA.