An <i>Arabidopsis</i> gene encoding an α-xylosyltransferase involved in xyloglucan biosynthesis
Bibliographic record
Abstract
Microsomal membranes catalyze the formation of xyloglucan from UDP-Glc and UDP-Xyl by cooperative action of alpha-xylosyltransferase and beta-glucan synthase activities. Here we report that etiolated pea microsomes contain an alpha-xylosyltransferase that catalyzes the transfer of xylose from UDP-[(14)C]xylose onto beta(1,4)-linked glucan chains. The solubilized enzyme had the capacity to transfer xylosyl residues onto cello-oligosaccharides having 5 or more glucose residues. Analysis of the data from these biochemical assays led to the identification of a group of Arabidopsis genes and the hypothesis that one or more members of this group may encode alpha-xylosyltransferases involved in xyloglucan biosynthesis. To evaluate this hypothesis, the candidate genes were expressed in Pichia pastoris and their activities measured with the biochemical assay described above. One of the candidate genes showed cello-oligosaccharide-dependent xylosyltransferase activity. Characterization of the radiolabeled products obtained with cellopentaose as acceptor indicated that the pea and the Arabidopsis enzymes transfer the (14)C-labeled xylose mainly to the second glucose residue from the nonreducing end. Enzymatic digestion of these radiolabeled products produced results that would be expected if the xylose was attached in an alpha(1,6)-linkage to the glucan chain. We conclude that this Arabidopsis gene encodes an alpha-xylosyltransferase activity involved in xyloglucan biosynthesis.
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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 | 0.001 |
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".