Deracemization of 2-Methyl-1,2,3,4-Tetrahydroquinoline Using Mutant Cyclohexylamine Oxidase Obtained by Iterative Saturation Mutagenesis
Bibliographic record
Abstract
The current toolkit of biocatalysts for the production of enantiomerically pure chiral amines is largely restricted to amine transaminases, ammonia lyases, or the genetic variants of monoamine oxidase N(MAO-N) from Aspergillus niger . Flavin-dependent amine oxidases have the apparent advantage of using molecular oxygen as a stoichiometric oxidant and their reactions are irreversible. To expand the toolkit and increase the substrate spectrum of a bacterial and flavin-dependent cyclohexylamine oxidase (CHAO) to enable deracemization of secondary amines, saturation mutagenesis of 11 amino acid residues located around the cyclohexanone substrate within a distance of 5 Å, followed by iterative saturation mutagenesis of four beneficial mutants, were performed. Screening with 2-methyl-1,2,3,4-tetrahydroquinoline as the substrate generated two improved CHAO variants, T198FL199S and T198FL199SM226F, that exhibited up to 406 times higher catalytic efficiency than the wild-type CHAO. Besides, high stereoselectivity for 2-methyl-1,2,3,4-tetrahydroquinoline and other 2-substituted-1,2,3,4-tetrahydroquinolines was demonstrated. In particular, deracemization of 2-methyl-1,2,3,4-tetrahydroquinoline by Escherichia coli whole cells expressing CHAO mutant T198FL199SM226F led to the production of ( R )-2-methyl-1,2,3,4-tetrahydroquinoline with high yield (76%) and enantiomeric excess (ee, 98%). Tetrahydroquinolines are important building blocks of natural and synthetic products useful in the pharmaceutical and agrochemical industries.
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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) | 0.001 | 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".