# Formation, metabolism and cell signaling actions of tryptophan catabolism-derived electrophiles

> **NIH NIH R35** · UNIVERSITY OF ALABAMA AT BIRMINGHAM · 2024 · $371,250

## Abstract

Under steady-state conditions, >90% of tryptophan (Trp) catabolism occurs in the liver via the kynurenine (Kyn)
pathway. However, this process has important pathophysiological roles in the brain, kidneys and heart, as well
as in modulating immunity, tumor microenvironments, and pregnancy. Altered Kyn metabolism is observed in
aging, cardiovascular disease, organ injury, cancer, and transplantation, where it often is a strong predictor of
outcome. Despite their relevance, the mechanisms behind the effects resulting from changes in systemic and
local Kyn metabolism are poorly defined. Using untargeted and targeted mass spectrometry together with
isotopically labeled standards, we discovered the endogenous formation of the electrophilic mediator kynurenine-
carboxyketoalkene (Kyn-CKA) secondary to in vivo Kyn deamination in humans and mice. Kyn-CKA reacts
covalently with cysteine residues in transcription factors, transcriptional regulatory proteins and enzymes to
regulate protein and cellular function. We recently published that Kyn-CKA modulates TLR/NF-κB- and
Keap1/Nrf2-dependent signaling and our preliminary data shows that Kyn-CKA also affects bioenergetic
metabolism and impacts seemingly cysteine-independent processes. Furthermore, we now know that N-formyl-
kynurenine (NFK) and 3-hydroxy-kynurenine (OH-Kyn) also generate electrophiles in vivo. We hypothesize that
Trp catabolism via the Kyn pathway results in the formation of novel bioactive products that adaptively modulate
cellular responses via redox-dependent mechanisms. We propose to characterize the mechanisms that regulate
the formation of Trp-derived electrophiles via modulation of individual enzymes in the Kyn pathway and the
identification of potential enzymes capable of catalyzing NFK, Kyn and OH-Kyn deamination. Trp-derived
electrophiles undergo conjugation to glutathione and reductive inactivation, thus we will identify and kinetically
characterize the enzymes involved in these processes. Unbiased high resolution mass spectrometry and
isotopically labeled precursors will be used to discover pathways for inactivation and biotransformation of Trp-
derived electrophiles. Furthermore, we will characterize the effects of Trp-derived electrophiles on cellular and
tissue bioenergetic metabolism, first using hepatocytes and then expanding to other cell types as informed by in
vivo formation data. In this regard, we will establish the impact of dietary Trp intake regulation on systemic and
tissue Trp-derived electrophile levels, as well as assess a potential contribution of the microbiome to this process.
Finally, we will use spatial transcriptomics in conjunction with click chemistry-dependent labeling strategies to
elucidate the sites of azido-Kyn deamination in vivo and define the impact of this process on electrophile-targeted
and untargeted regions of interest to differentiate between proximal and paracrine signaling effects. Overall, our
discovery that the Kyn pathway is a source of ...

## Key facts

- **NIH application ID:** 10764489
- **Project number:** 1R35GM152083-01
- **Recipient organization:** UNIVERSITY OF ALABAMA AT BIRMINGHAM
- **Principal Investigator:** Dario A Vitturi
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $371,250
- **Award type:** 1
- **Project period:** 2024-07-01 → 2029-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10764489

## Citation

> US National Institutes of Health, RePORTER application 10764489, Formation, metabolism and cell signaling actions of tryptophan catabolism-derived electrophiles (1R35GM152083-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10764489. Licensed CC0.

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