Rubisco supplies pyruvate for the 2- <i>C</i> -methyl-D-erythritol-4-phosphate pathway
Bibliographic record
Abstract
Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) produces pyruvate in the chloroplast through beta-elimination of the aci-carbanion intermediate. Here we show that this side reaction supplies pyruvate for isoprenoid, fatty acid, and branched chain amino acid biosynthesis in photosynthetically active tissue. 13C labeling studies of whole Arabidopsis plants demonstrate that the total carbon commitment to pyruvate is too large for phosphoenolpyruvate (PEP) to serve as precursor. Low oxygen stimulates rubisco carboxylase activity and increased pyruvate production and flux through the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway, which supplies the precursors for plastidic isoprenoid biosynthesis. Metabolome analysis of mutants defective in PEP or pyruvate import further supported rubisco as the main source of pyruvate in chloroplasts. Rubisco beta-elimination leading to pyruvate constituted 0.7% of the product profile in in vitro assays, which translates to 2% of the total carbon leaving the Calvin-Benson-Bassham cycle (CBC). These insights solve the so-called pyruvate paradox, improve the fit of metabolic models for central metabolism, and connect the MEP pathway directly to carbon assimilation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.002 |
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 source (direct Gemma or distilled Codex), 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".