FlaA1, a New Bifunctional UDP-GlcNAc C6Dehydratase/ C4 Reductase from Helicobacter pylori
Bibliographic record
Abstract
FlaA1 is a small soluble protein of unknown function in Helicobacter pylori. It has homologues that are essential for the virulence of numerous medically relevant bacteria. FlaA1 was overexpressed as a histidine-tagged protein and purified to homogeneity by nickel chelation and cation exchange chromatography. Spectrophotometric assays, capillary electrophoresis, and mass spectrometry analyses showed that FlaA1 is a novel bifunctional C(6) dehydratase/C(4) reductase specific for UDP-GlcNAc. It converts UDP-GlcNAc into a UDP-4-keto-6-methyl-GlcNAc intermediate, which is stereospecifically reduced into UDP-QuiNAc. Substrate conversions as high as 80% were obtained at equilibrium. The K(m) and V(max) for UDP-GlcNAc were 159 microm and 65 pmol/min, respectively. No exogenous cofactor was required to obtain full activity of FlaA1. Additional NADH was only used with poor efficiency for the reduction step. The biochemical characterization of FlaA1 is important for the elucidation of biosynthetic pathways that lead to the formation of 2,6-deoxysugars in medically relevant bacteria. It establishes unambiguously the first step of the pathway and provides the means of preparing the substrate UDP-QuiNAc, which is necessary for the study of downstream enzymes.
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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) | 0.000 | 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".