Conversion of Trypsin into a Na<sup>+</sup>-Activated Enzyme<sup>,</sup>
Bibliographic record
Abstract
Serine proteases of the chymotrypsin family show a dichotomous amino acid distribution for residue 225. Enzymes carrying Tyr at position 225 are activated by Na(+), whereas those carrying Pro are devoid of Na(+) binding and activation. Previous studies have demonstrated that the Y225P conversion is sufficient to abrogate Na(+) activation in several enzymes. However, the reverse substitution P225Y is necessary but not sufficient to introduce Na(+) binding and activation. Here we report that Streptomyces griseus trypsin, carrying Pro-225, can be engineered into a Na(+)-activated enzyme by replacing residues in the 170, 186, and 220 loops to those of coagulation factor Xa. The findings represent the first instance of an engineered Na(+)-activated enzyme and a proof of principle that should enable the design of other proteases with enhanced catalytic activity and allosteric regulation mediated by monovalent cation binding.
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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) | 0.000 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".