Substrate recognition by three family 13 yeast α‐glucosidases
Why this work is in the frame
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Bibliographic record
Abstract
Important hydrogen bonding interactions between substrate OH-groups in yeast alpha-glucosidases and oligo-1,6-glucosidase from glycoside hydrolase family 13 have been identified by measuring the rates of hydrolysis of methyl alpha-isomaltoside and its seven monodeoxygenated analogs. The transition-state stabilization energy, DeltaDeltaG, contributed by the individual OH-groups was calculated from the activities for the parent and the deoxy analogs, respectively, according to DeltaDeltaG = -RT ln[(Vmax/Km)analog/(Vmax/Km)parent]. This analysis of the energetics gave DeltaDeltaG values for all three enzymes ranging from 16.1 to 24.0 kJ.mol-1 for OH-2', -3', -4', and -6', i.e. the OH-groups of the nonreducing sugar ring. These OH-groups interact with enzyme via charged hydrogen bonds. In contrast, OH-2 and -3 of the reducing sugar contribute to transition-state stabilization, by 5.8 and 4.1 kJ.mol-1, respectively, suggesting that these groups participate in neutral hydrogen bonds. The OH-4 group is found to be unimportant in this respect and very little or no contribution is indicated for all OH-groups of the reducing-end ring of the two alpha-glucosidases, probably reflecting their exposure to bulk solvent. The stereochemical course of hydrolysis by these three members of the retaining family 13 was confirmed by directly monitoring isomaltose hydrolysis using 1H NMR spectroscopy. Kinetic analysis of the hydrolysis of methyl 6-S-ethyl-alpha-isomaltoside and its 6-R-diastereoisomer indicates that alpha-glucosidase has 200-fold higher specificity for the S-isomer. Substrate molecular recognition by these alpha-glucosidases are compared to earlier findings for the inverting, exo-acting glucoamylase from Aspergillus niger and a retaining alpha-glucosidase of glycoside hydrolase family 31, respectively.
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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