In Vivo Regulatory Phosphorylation of Novel Phospho<i>enol</i>pyruvate Carboxylase Isoforms in Endosperm of Developing Castor Oil Seeds
Bibliographic record
Abstract
Our previous research characterized two phosphoenolpyruvate (PEP) carboxylase (PEPC) isoforms (PEPC1 and PEPC2) from developing castor oil seeds (COS). The association of a shared 107-kD subunit (p107) with an immunologically unrelated bacterial PEPC-type 64-kD polypeptide (p64) leads to marked physical and kinetic differences between the PEPC1 p107 homotetramer and PEPC2 p107/p64 heterooctamer. Here, we describe the production of antiphosphorylation site-specific antibodies to the conserved p107 N-terminal serine-6 phosphorylation site. Immunoblotting established that the serine-6 of p107 is phosphorylated in COS PEPC1 and PEPC2. This phosphorylation was reversed in vitro following incubation of clarified COS extracts or purified PEPC1 or PEPC2 with mammalian protein phosphatase type 2A and is not involved in a potential PEPC1 and PEPC2 interconversion. Similar to other plant PEPCs examined to date, p107 phosphorylation increased PEPC1 activity at pH 7.3 by decreasing its K(m)(PEP) and sensitivity to L-malate inhibition, while enhancing glucose-6-P activation. By contrast, p107 phosphorylation increased PEPC2's K(m)(PEP) and sensitivity to malate, glutamic acid, and aspartic acid inhibition. Phosphorylation of p107 was promoted during COS development (coincident with a >5-fold increase in the I(50) [malate] value for total PEPC activity in desalted extracts) but disappeared during COS desiccation. The p107 of stage VII COS became fully dephosphorylated in planta 48 h following excision of COS pods or following 72 h of dark treatment of intact plants. The in vivo phosphorylation status of p107 appears to be modulated by photosynthate recently translocated from source leaves into developing COS.
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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 | 0.000 |
| 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 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".