Temperature and phosphate effects on allosteric phenomena of phosphofructokinase from a hibernating ground squirrel (Spermophilus lateralis)
Bibliographic record
Abstract
Temperature effects on the kinetic properties of phosphofructokinase (PFK) purified from skeletal muscle of the golden-mantled ground squirrel, Spermophilus lateralis, were examined at 37 degrees C and 5 degrees C, values characteristic of body temperatures in euthermia vs. hibernation. The enzyme showed reduced sensitivity to all activators at 5 degrees C, the K(a) values for AMP, ADP, NH(4) (+) and F2,6P(2) were 3-11-fold higher at 5 degrees C than at 37 degrees C. Inhibition by citrate was not affected whereas phosphoenolpyruvate, ATP and urea became more potent inhibitors at low temperature. While typically considered an activator of PFK activity, inorganic phosphate performed as an inhibitor at 5 degrees C. Decreasing temperature alone causes the actions of inorganic phosphate to change from activation to inhibition. We found that K(m) values for ATP remained constant while V(max) dropped significantly upon the addition of phosphate. Phosphate inhibition at 5 degrees C was noncompetitive with respect to ATP and the K(i) was 0.15 +/- 0.01 mm (n = 4). The results indicate that PFK is less likely to be activated in cold torpid muscle; PFK is less sensitive to changing adenylate levels at the low temperatures characteristic of torpor, and PFK is clearly much less sensitive to biosynthetic signals. All of these characteristics of hibernator PFK would serve to reduce glycolytic rate and help to preserve carbohydrate reserves during torpor.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| 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".