Characterization of an ornithine N <sup>5</sup> ‐hydroxylase involved in pyoverdine siderophore biosynthesis in <i>Pseudomonas aeruginosa</i>
Bibliographic record
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that infects individuals with cystic fibrosis or those that are immuno‐compromised. It produces the siderophore pyoverdine that enables it to acquire iron, an essential growth element, from tightly bound iron stores within the human host. The formation of the iron‐chelating hydroxamate functional group in pyoverdine requires the enzyme PvdA, a flavin‐dependent oxygenase, that catalyzes the N 5 ‐hydroxylation of L‐ornithine. pvd A from P. aeruginosa was successfully overexpressed in E. coli and the enzyme purified. In the absence of L‐ornithine, PvdA possessed an NADPH oxidase activity of 0.088 μmolmin −1 mg −1 . The substrate L‐ornithine stimulated this activity by a factor of 10, and the reaction was tightly coupled to the formation of the hydroxylamine. Steady‐state kinetic analysis showed that the L‐ornithine dependent NADPH oxidation obeys Michaelis‐Menten kinetics with apparent K m and V max values of 0.66 mM and 0.85Umg −1 , respectively. L‐lysine was a non‐substrate effector that stimulated NADPH oxidation but was not hydroxylated by the enzyme. L‐norleucine, L‐glutamine and L‐arginine were not substrates or effectors, but they were competitive inhibitors of the L‐ornithine dependent NADPH oxidation reaction, with K ic between 0.4mM and 6.4mM. The results indicate that binding of compounds to the effector site of PvdA is not sufficient to stimulate the NADPH oxidation activity.
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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) | 0.000 | 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".