Purification and Characterization of Polyphenol Oxidase from Callus Cultures of Portulaca grandiflora.
Bibliographic record
Abstract
Three isoforms of polyphenol oxidase (I-a, I-b and II) were purified from betacyanin-producing callus cultures of Portulaca grandiflora, by ammonium sulfate precipitation followed by successive column chromatographies of DEAE cellulose, Sephacryl S-200, hydroxyapatite and Mono-Q. The molecular masses of the monomeric polyphenol oxidase I-a and I-b were calculated to be 66 and 65 kDa, respectively, when analyzed by SDS-PAGE. Polyphenol oxidase II appeared to be a heterodimer of two subunits with molecular masses of 25 and 27 kDa. The optimal pH for polyphenol oxidase activity of I-a and I-b was 5.0, and for II was 6.0. These enzymes were markedly inhibited by sulfhydryl binding reagents, ascorbate, kojic acid, copper-chelating reagents and Fe2+. L-DOPA (L-3, 4-dihydroxyphenylalanin) was a good substrate for these enzymes, although no activity with tyrosine and hydroquinone was observed. The apparent Km values of polyphenol oxidase I-a, I-b and II for DOPA were 2.0, 2.2 and 3.5mM, respectively. No monophenol oxidase (tyrosine hydroxylation) activity by these enzymes was observed.
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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 | 0.001 |
| 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".