Oxidation of four monoterpenoid indole alkaloid classes by three cytochrome P450 monooxygenases from <i>Tabernaemontana litoralis</i>
Bibliographic record
Abstract
Cytochrome P450 monooxygenases (CYPs) are well known for their ability to catalyze diverse oxidation reactions, playing a significant role in the biosynthesis of various natural products. In the realm of monoterpenoid indole alkaloids (MIAs), one of the largest groups of alkaloids in nature, CYPs are integral to reactions such as hydroxylation, epoxidation, ring opening, ring rearrangement, and aromatization, contributing to the extensive diversification of these compounds. In this study, we investigate the transcriptome, metabolome, and MIA biosynthesis in Tabernaemontana litoralis (milky way tree), a prolific producer of rare pseudoaspidosperma-type MIAs. Alongside known pseudoaspidosperma biosynthetic genes, we identify and characterize three new CYPs that facilitate regio- and stereospecific oxidation of four MIA skeletons: iboga, aspidosperma, pseudoaspidosperma, and quebrachamine. Notably, the tabersonine 14,15-β-epoxidase catalyzes the formation of pachysiphine, the stereoisomer of 14,15-α-epoxytabersonine (lochnericine) found in Catharanthus roseus (Madagascar periwinkle) roots. The pseudovincadifformine 18-hydroxylase is the first CYP identified to modify a pseudoaspidosperma skeleton. Additionally, we demonstrate that the enzyme responsible for C10-hydroxylation of the iboga MIA coronaridine also catalyzes C10-hydroxylation of voaphylline, which bears a quebrachamine skeleton. With the discovery of a new MIA, 11-hydroxypseudovincadifformine, this study provides a comprehensive understanding of MIA biosynthesis and diversification in T. litoralis, highlighting its potential for further exploration.
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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".