Cloning and Characterization of Mouse Nucleoside Triphosphate Diphosphohydrolase-8<sup>,</sup>
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Bibliographic record
Abstract
A novel mammalian plasma membrane bound nucleoside triphosphate diphosphohydrolase (NTPDase), named NTPDase8, has been cloned and characterized. Analysis of cDNA reveals an open reading frame of 1491 base pairs encoding a protein of 497 amino acid residues with an estimated molecular mass of 54650 Da and a predicted isoelectric point of 5.94. In a mouse, the genomic sequence is located on chromosome 2A3 and is comprised of 10 exons. The deduced amino acid sequence reveals eight putative N-glycosylation sites, two transmembrane domains, five apyrase-conserved regions, and 20-50% amino acid identity with other mammalian NTPDases. mRNA expression was detected in liver, jejunum, and kidney. Both intact cells and crude cell lysates from COS-7 cells expressing NTPDase8 hydrolyzed P2 receptor agonists, namely, ATP, ADP, UTP, and UDP, but did not hydrolyze AMP. There was an absolute requirement for divalent cations for the catalytic activity (Ca(2+) > Mg(2+)) with an optimal pH between 5.5 and 8.0 for ATP and 6.4 for ADP hydrolysis. Kinetic parameters derived from analysis of crude cell lysates showed that the enzyme had lower apparent K(m) values for adenine nucleotides and for triphosphonucleosides (K(m,app) of 13 microM for ATP, 41 microM for ADP, 47 microM for UTP, and 171 microM for UDP). Hydrolysis of triphosphonucleosides resulted in a transient accumulation of the corresponding diphosphonucleoside, as expected from the apparent K(m) values. Enzymatic properties of NTPDase8 differ from those of other NTPDases suggesting an alternative way to modulate nucleotide levels and consequently P2 receptor activation.
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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 it