Structural and functional insights into extreme thermal stability and activity of two <scp>GH</scp> 12 domains of a multidomain glycosidase from a hyperthermophilic euryarchaeon
Bibliographic record
Abstract
Bacteria and fungi are well known for efficient degradation of plant polysaccharides thanks to various enzymes involved in plant cell wall decomposition. However, little is known about the role of archaea in this process or the repertoire and features of their polysaccharide‐degrading enzymes. In our previous work, we discovered an archaeal multidomain glycosidase (MDG) composed of three catalytic domains (GH5 and two GH12) and two cellulose‐binding modules (CBM2). The recombinant MDG and individual GH5 catalytic domain were active against cellulose and a number of other polysaccharides at a wide range of temperatures, with optimum temperatures ( T opt ) of 60 °C and 80 °C, respectively. The present study was focused on the characterization of two GH12 domains of the MDG. Purified recombinant TMDG_GH12‐1 and TMDG_GH12‐2 proteins were active as individual enzymes but exhibited distinct catalytic properties. Both enzymes were thermostable and active at extremely high temperatures: TMDG_GH12‐1 was active at 40–130 °C ( T opt 100 °C), and its half‐life ( t ½ ) at 100 °C was 42 h, which makes it one of the most thermostable glycosidases known so far, whereas TMDG_GH12‐2 was active at 50–100 °C ( T opt 90 °C) with t ½ at 100 °C being 30 min. Phylogenetic and structural analysis of both TMDG_GH12 proteins together with molecular docking and site‐directed mutagenesis suggested that the presence of two disulfide bridges and the W → Q mutation in the active site contribute to the exceptional thermostability of TMDG_GH12‐1. Further structural and mutational studies of the TMDG_GH12‐1 domain will help to gain a better understanding of the molecular mechanisms of its extraordinary thermostability and substrate specificity.
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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".