Kinetics, substrate specificity, and stereospecificity of two new protein tyrosine phosphatase-like inositol polyphosphatases from <i>Selenomonas lacticifex</i>
Bibliographic record
Abstract
Inositol polyphosphatases (IPPases) play an important role in the metabolism of inositol polyphosphates, a class of molecules involved in signal transduction. Here we characterize 2 new protein tyrosine phosphatase-like IPPases (PhyAsl and PhyBsl) cloned from Selenomonas lacticifex that can hydrolyze myo-inositol hexakisphosphate (InsP6) in vitro. To determine their preferred substrates and stereospecificity of InsP6 dephosphorylation, a combination of kinetic and high-performance ion pair chromatography studies were conducted. Despite only 33% amino acid sequence identity between them, both enzymes display strict specificity for IPP substrates and cleave InsP6 primarily at the D-3-phosphate position (>90%). Furthermore, both enzymes predominantly degrade InsP6 to Ins(2)P via identical and very specific routes of dephosphorylation (3,4,5,6,1). Despite these similarities, PhylAsl is shown to have a slight kinetic preference for the major inositol pentakisphosphate intermediate in its InsP6 hydrolysis pathway, whereas PhyBsl displays a unique and substantial preference for an inositol tetrakisphosphate intermediate.
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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".