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takyon writes:

Researchers have demonstrated that an enzyme-free metabolic pathway using sulfate radicals can mirror the Krebs cycle:

A set of biochemical processes crucial to cellular life on Earth could have originated in chemical reactions taking place on the early Earth four billion years ago, believes a group of scientists from the Francis Crick Institute and the University of Cambridge. The researchers have demonstrated a network of chemical reactions in the lab which mimic the important Krebs cycle present in living organisms today. In a study published in the journal Nature Ecology and Evolution, they say it could explain an important step in how life developed on Earth.

[...] One central metabolic pathway learned by every A-level biology student is the Krebs cycle. But how did this essential set of chemical reactions, each step catalyzed by an enzyme, first arise? Each step in the cycle is not enough by itself. Life needs a sequence of these reactions, and it would have needed it before biological enzymes were around: Amino acids, the molecular components of enzymes, are made from products of the Krebs cycle.

The research group from the Francis Crick Institute and the University of Cambridge say their demonstration offers an answer. They have shown an enzyme-free metabolic pathway that mirrors the Krebs cycle. It is sparked by particles called sulphate radicals under conditions similar to those on Earth four billion years ago. Senior author Dr Markus Ralser of the Francis Crick Institute and University of Cambridge explains: "This non-enzymatic precursor of the Krebs cycle that we have demonstrated forms spontaneously, is biologically sensible and efficient. It could have helped ignite life four billion years ago."

Found at ScienceDaily.

Sulfate radicals enable a non-enzymatic Krebs cycle precursor (open, DOI: 10.1038/s41559-017-0083) (DX)

Original Submission