The basic architecture of the modern metabolic network could have originated from the chemical and physical constraints that existed on Earth billions of years ago
- Markus Ralser
In a study funded by the Wellcome Trust and the European Research Council, researchers at the University of Cambridge reconstructed the chemical make-up of the Earth’s earliest ocean in the laboratory. The team found the spontaneous occurrence of reaction sequences which in modern organisms enable the formation of molecules essential for the synthesis of metabolites. These organic molecules, such as amino acids, nucleic acids and lipids, are critical for the cellular metabolism seen in all living organisms
The detection of one of the metabolites, ribose 5-phosphate, in the reaction mixtures is particularly noteworthy, as RNA precursors like this could in theory give rise to RNA molecules that encode information, catalyze chemical reactions and replicate.
It was previously assumed that the complex metabolic reaction sequences, known as metabolic pathways, which occur in modern cells, were only possible due to the presence of enzymes. Enzymes are highly complex molecular machines that are thought to have come into existence during the evolution of modern organisms. However, the team’s reconstruction reveals that metabolism-like reactions could have occurred naturally in our early oceans, before the first organisms evolved.
Life on Earth began during the Archean geological eon almost 4 billion years ago in iron-rich oceans that dominated the surface of the planet. This was an oxygen-free world, pre-dating photosynthesis, when the redox state of iron was different and much more soluble to act as potential catalysts. In these oceans, iron, other metals and phosphate facilitated a series of reactions which resemble the core of cellular metabolism occurring in the absence of enzymes.
The findings suggest that metabolism predates the origin of life and evolved through the chemical conditions that prevailed in the world's earliest oceans.
Read the full story
Image: After storm
Credit: Dhilung Kirat
Reproduced courtesy of the University of Cambridge
____________________________________________