α,β-Dicarbonyl reduction is mediated by the<i>Saccharomyces</i>Old Yellow Enzyme
Bibliographic record
Abstract
The undesirable flavor compounds diacetyl and 2,3-pentanedione are vicinal diketones (VDKs) formed by extracellular oxidative decarboxylation of intermediate metabolites of the isoleucine, leucine and valine (ILV) biosynthetic pathway. These VDKs are taken up by Saccharomyces and enzymatically converted to acetoin and 3-hydroxy-2-pentanone, respectively. Purification of a highly enriched diacetyl reductase fraction from Saccharomyces cerevisiae in conjunction with mass spectrometry identified Old Yellow Enzyme (Oye) as an enzyme capable of catalyzing VDK reduction. Kinetic analysis of recombinant Oye1p, Oye2p and Oye3p isoforms confirmed that all three isoforms reduced diacetyl and 2,3-pentanedione in an NADPH-dependent reaction. Transcriptomic analysis of S. cerevisiae (ale) and S. pastorianus (lager) yeast during industrial fermentations showed that the transcripts for OYE1, OYE2, arabinose dehydrogenase (ARA1), α-acetolactate synthase (ILV2) and α-acetohydroxyacid reductoisomerase (ILV5) were differentially regulated in a manner that correlated with changes in extracellular levels of VDKs. These studies provide insights into the mechanism for reducing VDKs and decreasing maturation times of beer which are of commercial importance.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.006 | 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; both teacher heads agree on what is shown here.
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".