Purification and characterization of a 4-hydroxybenzoate decarboxylase from an anaerobic coculture
Bibliographic record
Abstract
The oxygen-sensitive 4-hydroxybenzoate decarboxylase (4OHB-DC) activity from a phenol-carboxylating coculture, consisting of Clostridium-like strain 6 and an unidentified strain 7, was studied. Assays done with cell extracts showed that the optimal pH was 5.0-6.5 and the K m was 5.4 mM. The activity decreased by 50% in the presence of 5 mM EDTA, and it was restored and even enhanced by the addition of Mg ++ , Mn ++ , Zn ++ , or Ca ++ . After purification, the molecular mass of the enzyme was estimated as 420 kDa by gel chromatography, and as 119 kDa by SDS-PAGE, suggesting a homotetrameric structure. Its pI was 5.6. The N-terminal amino acid sequence showed 95% and 76% homology with the pyruvate-flavodoxin oxidoreductase (nifJ gene product) from Enterobacter agglomerans and Klebsiella pneumoniae, respectively. The purified enzyme also slowly catalyzed the reverse reaction, that is the phenol carboxylation. These characteristics suggest that this enzyme is different from other known decarboxylases. This includes the 4OHB-DC from Clostridium hydroxybenzoicum, which is the only one that had been purified before.Key words: purification, 4-hydroxybenzoate decarboxylase, coculture, phenol carboxylation, anaerobic conditions.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".