Enzymatic activity of Campylobacter jejuni hippurate hydrolase
Bibliographic record
Abstract
The hippurate hydrolase enzyme of Campylobacter jejuni was expressed in Escherichia coli as a six-histidine-tagged fusion protein. The purified recombinant enzyme was characterized to gain an understanding of the structure and activity of the hippurate hydrolase. The recombinant enzyme had a native molecular mass of 193+/- 11 kDa a reduced molecular mass of 42.4+/- 0.8 kDa, and possessed 1.98+/- 0.68 molecules of zinc per enzyme subunit molecule, suggesting that it was a homotetramer with two associated zinc ions. The enzyme was a metallocarboxypeptidase that was sensitive to silver, copper and ferrous ions, and displayed optimal activity at pH 7.5 and 50 degrees C. It hydrolyzed carboxypeptidase substrates in vitro, displaying its highest activity against N-benzoyl-linked small aliphatic amino acids. A high proportion of the enzyme structure consisted of highly ordered alpha-helix and beta-sheet sequences. An alignment of the amino acid sequence of the hippurate hydrolase enzyme with those of related enzymes with similar activities revealed several conserved amino acids, which might be involved in enzyme catalysis or metal ion binding for the enzyme. Site-directed mutagenesis of the recombinant enzyme demonstrated that the Asp(76), Aps(104), Glu(134), Glu(135), His(161) and His(356) positions were important for the catalytic activity of the enzyme.
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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 | 0.000 |
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".