Evidence for corrin biosynthesis in the last universal common ancestor

Area of Science:

• Biochemistry
• Evolutionary Biology
• Astrobiology

Background:

• Corrinoids, like vitamin B12, are vital cofactors in essential metabolic pathways.
• The acetyl-CoA pathway, a primitive CO2 fixation method, relies on cobamides and the corrinoid iron-sulfur protein (CoFeS).
• CoFeS is found in ancient archaeal methanogens and bacterial acetogens, suggesting deep evolutionary roots for corrinoids.

Purpose of the Study:

• To investigate the evolutionary origin of corrin biosynthesis and its relation to the divergence of archaea and bacteria.
• To determine if corrin pathways arose independently or were transferred between lineages.
• To understand the role of corrinoids in early life and CO2 assimilation.

Main Methods:

• Phylogenetic analysis of 26 enzymes involved in corrin ring and lower ligand biosynthesis.
• Structural data analysis of key enzymes.
• Comparison with known biochemical pathways and evolutionary models.

Main Results:

• Cobamide synthesis pathways trace back to the last universal common ancestor of all life (LUCA).
• Pterin-dependent methyl synthesis pathways likely evolved independently in archaeal and bacterial lineages after LUCA.
• Corrin biosynthesis enzymes were recruited from pre-existing ancient pathways.

Conclusions:

• Corrin biosynthesis is ancient, predating the divergence of archaea and bacteria, and likely originated in LUCA.
• Enzymatic corrin biosynthesis may have replaced abiotic mineral catalysts in early CO2 assimilation.
• Corrin synthesis is implicated in the origin of free-living cells and early life on Earth.