EXPLORING THE ROLE OF THE DUAL-TARGETED 'MAMMALIAN TYPE' PURPLE ACID PHOSPHATASE ATPAP17 IN ARABIDOPSIS THALIANA PHOSPHATE AND ROS METABOLISM
Bibliographic record
Abstract
Secreted and intracellular purple acid phosphatases (APases) play a central role in the recycling and acquisition of inorganic phosphate (Pi), a limiting macronutrient that is vital for plant growth. In mammals, a single low molecular weight (LMW) secreted purple APase (PAP) isozyme (e.g. HsACP5 in humans) is expressed that exhibits bifunctional phosphatase and peroxidase (PRx) activities to support dual roles in dephosphorylating extracellular bone matrix phosphoproteins or generating reactive oxygen species (ROS) for immune-related pathogen defense. Similarly, AtPAP17 (At3g17790), one of twenty-nine predicted Arabidopsis PAP isozymes, is a LMW (35 kDa) HsACP5 ortholog that exhibits APase and PRx activity. A 35 kDa monomeric PAP was unexpectedly purified from cell wall (CW) extracts of Pi-starved (–Pi) suspension cell cultures of the model plant Arabidopsis thaliana and identified as AtPAP17 (At3g17790). AtPAP17 was de novo synthesized and dual-targeted to the secretome and/or intracellular fraction of –Pi or salt stressed, or senescing leaves of Arabidopsis. Transiently expressed AtPAP17-GFP localized to lytic vacuoles of the Arabidopsis cells. No discernible biochemical or phenotypical changes associated with AtPAP17 loss of function in an atpap17 mutant occurred during Pi deprivation, leaf senescence, or salinity stress. Nevertheless, AtPAP17 is hypothesized to contribute to Pi metabolism owing to its marked upregulation during Pi starvation and leaf senescence, broad APase substrate selectivity and pH-activity profile, and rapid repression and turnover following Pi-resupply to –Pi plants. While AtPAP17 also catalyzed the peroxidation of luminol, which was optimal at pH 9.2, it exhibited a low Vmax and affinity for H2O2 relative to horseradish peroxidase. These results, coupled with absence of a phenotype in the –Pi or salt stressed atpap17 mutant, do not support proposals that AtPAP17’s PRx activity contributes to the detoxification of ROS during stresses that trigger AtPAP17 upregulation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 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 teacher head, 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".