Conversion of pyridoxal to pyridoxamine with <scp>NH</scp> <sub>3</sub> and <scp>H</scp> <sub>2</sub> on nickel generates a protometabolic nitrogen shuttle under serpentinizing conditions
Bibliographic record
Abstract
Serpentinizing hydrothermal vents are likely sites for the origin of metabolism because they produce H 2 as a source of electrons for CO 2 reduction while depositing zero‐valent iron, cobalt, and nickel as catalysts for organic reactions. Recent work has shown that solid‐state nickel can catalyze the H 2 ‐dependent reduction of CO 2 to various organic acids and their reductive amination with H 2 and NH 3 to biological amino acids under the conditions of H 2 ‐producing hydrothermal vents and that amino acid synthesis from NH 3 , H 2 , and 2‐oxoacids is facile in the presence of Ni 0 . Such reactions suggest a metallic origin of metabolism during early biochemical evolution because single metals replace the function of over 130 enzymatic reactions at the core of metabolism in microbes that use the acetyl‐CoA pathway of CO 2 fixation. Yet solid‐state catalysts tether primordial amino synthesis to a mineral surface. Many studies have shown that pyridoxal catalyzes transamination reactions without enzymes. Here we show that pyridoxamine, the NH 2 ‐transferring intermediate in pyridoxal‐dependent transamination reactions, is generated from pyridoxal by reaction with NH 3 (as little as 5 m m ) and H 2 (5 bar) on Ni 0 as catalyst at pH 11 and 80 °C within hours. These conditions correspond to those in hydrothermal vents undergoing active serpentinization. The results indicate that at the origin of metabolism, pyridoxamine provided a soluble, organic amino donor for aqueous amino acid synthesis, mediating an evolutionary transition from NH 3 ‐dependent amino acid synthesis on inorganic surfaces to pyridoxamine‐dependent organic reactions in the aqueous phase.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".