Enzyme-free Krebs cycle: Big new find in the extrapolation of life
|March 25, 2017||Posted by News under News, Origin Of Life|
From Linda Geddes at New Scientist:
Metabolism may be older than life itself and start spontaneously
However, the enzyme-free Krebs cycle that Ralser observed isn’t the complete biochemical cycle as it operates in modern cells. That may have come later, after enzymes evolved.
Furthermore, the sulphate-driven cycle has so far only been shown to run in one direction (the oxidative one). In some species, the Krebs cycle can also run in reverse and help to incorporate CO2 into the building of new carbohydrates. Some think it may therefore have been involved in early carbon fixation, in which case you’d expect to see the cycle spontaneously turning in this direction too.
Until researchers can demonstrate both these things, they cannot claim that metabolism came before cells and life, some experts think.
“This is a neat paper and the findings are striking and careful,” says Nick Lane, an evolutionary biochemist at University College London. “But this is strictly the oxidative Krebs cycle, which is certainly not ancient. It probably became oxidative after the rise of molecular oxygen in the atmosphere. More.
The obvious problem with this Krebs cycle thesis and all the others is what they don’t explain: If there is a simple way life can just come into existence, why has no one been able to demonstrate abiogenesis (spontaneous origin of life) today?
See also: What we know and don’t know about the origin of life
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