Chemical Antiquity in Metabolism

Area of Science:

• Biochemistry and Astrobiology
• Origin of Life Studies
• Metabolic Pathway Evolution

Background:

• Life's origin involves exergonic chemical reactions, requiring carbon, energy, and electrons.
• The acetyl-CoA pathway is unique in simultaneously fulfilling these three metabolic needs.
• Previous research suggested the acetyl-CoA pathway's role in early metabolism and the catalytic importance of metals like Fe, Co, and Ni.

Purpose of the Study:

• To investigate the potential of native metals (Fe, Co, Ni) as catalysts for the acetyl-CoA pathway.
• To explore the role of serpentinizing hydrothermal vents in the origin of metabolism.
• To understand the evolutionary precursors of key metabolic components like electron transfer mechanisms.

Main Methods:

• Experimental reactions of H2 and CO2 with native Fe, Co, and Ni catalysts at 100°C under alkaline conditions.
• Analysis of reaction products including formate, acetate, methane, and pyruvate.
• Comparison of metal-catalyzed reactions with the enzymatic requirements of the natural acetyl-CoA pathway.

Main Results:

• Native Fe, Co, and Ni metals and their alloys efficiently catalyze the conversion of H2 and CO2 to pyruvate, acetate, and methane.
• These metal catalysts replace the function of over 120 enzymes typically required for the acetyl-CoA pathway.
• Alkaline conditions, found in serpentinizing hydrothermal vents, are optimal for these reactions and promote hydrogen oxidation.

Conclusions:

• The acetyl-CoA pathway's origin is strongly linked to H2-producing, serpentinizing hydrothermal vents and their native metal deposits.
• The simplicity and thermodynamic favorability of metal-catalyzed reactions support the bedrock antiquity of this metabolic pathway.
• The findings suggest an evolutionary precursor to flavin-based electron bifurcation in the reduction of ferredoxin by native iron, highlighting the ancient role of Fe-S clusters.