Energetics of amino acid synthesis in hydrothermal ecosystems

Thermodynamic calculations showed that the autotrophic synthesis of all 20 protein-forming amino acids was energetically favored in hot (100°C), moderately reduced, submarine hydrothermal solutions relative to the synthesis in cold (18°C), oxidized, surface seawater. The net synthesis reactions of 11 amino acids were exergonic in the hydrothermal solution, but all were endergonic in surface seawater. The synthesis of the requisite amino acids of nine thermophilic and hyperthermophilic proteins in a 100°C hydrothermal solution yielded between 600 and 8000 kilojoules per mole of protein, which is energy that is available to drive the intracellular synthesis of enzymes and other biopolymers in hyperthermophiles thriving in these ecosystems.