Equilibration of adenylates in the mitochondrial intermembrane space maintains respiration and regulates cytosolic metabolism
Bibliographic record
Abstract
Adenylate kinase (AK) uses one each of Mg-complexed and free adenylates as substrates in both directions of its reaction. It is very active in the mitochondrial intermembrane space (IMS), but is absent from the mitochondrial matrix where low [ADP] upon intensive respiration limits the respiratory rate. AK activity in the IMS is linked to ATP/ADP exchange across the inner mitochondrial membrane by using ATP (imported from the matrix) and AMP as substrates, the latter provided by apyrase and other AMP-generating reactions. The ADP formed by AK is exported to the matrix (in exchange for ATP), providing a mechanism for regeneration of ADP during respiration. From the AK equilibrium, and taking pH values characteristic of subcellular compartments, [Mg2+] in the IMS is calculated as 0.4-0.5 mM and in the cytosol as 0.2-0.3 mM, whereas the MgATP:MgADP ratio in the IMS and cytosol is 6-9 and 10-15, respectively. These represent optimal conditions for transport of adenylates (via the maintenance of an ATPfree:ADPfree ratio close to 1) and mitochondrial respiratory rates (via the maintenance of submillimolar [ADPfree] in the IMS). This, in turn, has important consequences for mitochondrial and cytosolic metabolism, including regulation of the protein phosphorylation rate (via changes in the MgATP:AMPfree ratio) and allosteric regulation of mitochondrial and cytosolic enzymes. Metabolomic consequences are discussed in connection with the calculation of metabolic fluxes from subcompartmental distributions of total adenylates and Mg2+.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".