Manganese (Mn<sup>2+</sup>)-Dependent Storage Stabilization of Rhodotorula glutinis Phenylalanine Ammonia-lyase Activity
Bibliographic record
Abstract
Phenylalanine ammonia-lyase (PAL; E C 4.3.1.5) reverse reaction has been exploited for the commercial production of optically pure l-phenylalanine from trans-cinnamic acid. Optimal conditions for the growth and PAL activity of Rhodotorula glutinis cells and an improved method for the synthesis of l-phenylalanine have been reported. A major problem encountered during these studies was rapid loss of PAL activity during storage of the yeast cells, which were therefore unsuitable for long-term and repeated use. Enhancement of enzyme stability in the presence of various additives including polyhydric compounds and metal ions is described. Whole cells retained nearly 85% of the original enzyme activity for at least 12 weeks when a low concentration of Mn2+ (0.01%) was included in the storage buffer medium (50 mM Tris-HCl, pH 8.8). In contrast, <3.0% activity was present in the control within 4 weeks. Mn2+-dependent stabilization of PAL was also observed with an isolated enzyme preparation (73% retention in activity for 12 weeks) obtained by ultrasonication of R. glutinis whole cells. The data suggest that Mn2+ ions may be responsible for the specific stabilization of a more active conformation of the enzyme. In addition, enzyme stability as a function of temperature was studied, and the optimal temperature for maximal activity retention was 0-2 degrees C. The effects of various additives on the induction of PAL have also been examined. These results could have direct implications in studies on activity, inhibition, and reaction mechanism of this biotechnologically important enzyme.
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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) | 0.000 | 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 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".