Yanthine
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| Properties | |
| C5H4N4O2 | |
| Molar mass | 152.113 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
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Yanthine (2,8-dioxopurine) is a key intermediate metabolite in the anaerobic reductive degradation pathway of uric acid by gut bacteria. It has emerged as a potential circulating biomarker for hyperuricemia and gout.[1][2]
Chemical properties
Yanthine has the molecular formula C₅H₄N₄O₂ with a molecular weight of 152.11 g/mol. The compound exhibits distinctive fluorescence properties with an excitation maximum at 308 nm and emission maximum at 363-379 nm (pH-dependent), which distinguishes it from structurally related purines such as uric acid, hypoxanthine, and xanthine.[1]
Biochemical role
The reductive uric acid degradation pathway
Yanthine is formed as the first intermediate in an anaerobic bacterial pathway for uric acid degradation, distinct from the well-characterized aerobic oxidative pathway. The complete pathway proceeds as follows:[1][2] Uric acid → Yanthine → Ureidomethyl-hydantoin → 2,3-Diureidopropionate → Albizziin → 2,3-Diaminopropionate → Pyruvate + Ammonia
Enzymatic formation
Yanthine is generated through reductive dehydroxylation of uric acid, catalyzed by xanthine dehydrogenase homologs:[1][2] In Escherichia coli, the XdhD-YgfM complex catalyzes this reaction. XdhD contains the molybdenum cofactor (MoCo)-binding hydroxylase site, while YgfM contains the FAD-binding site for electron transfer from NADH. A key structural difference in XdhD compared to canonical xanthine-oxidizing XdhA is the presence of glutamate 606 (E606) in the active site, which contributes to substrate orientation and yanthine formation.[1] In Clostridium species, XdhAC (also designated DOPDH - 2,8-Dioxopurine Dehydrogenase) is a selenium-dependent molybdenum hydroxylase that functions bidirectionally, both reducing uric acid to yanthine and oxidizing yanthine to uric acid. It uses alternative electron donors such as reduced ferredoxin or methylviologen.[2]
Further metabolism
Yanthine undergoes reductive dearomatization catalyzed by YgfK (in E. coli) or UacX (in Clostridioides difficile), both flavin-dependent reductases. The 8-oxo group in yanthine facilitates dearomatization of the imidazole ring. This reaction is thermodynamically coupled with hydrolytic cleavage by SsnA to form ureidomethyl-hydantoin as the major product.[1][2]
Genetic basis
The pathway is encoded by a conserved gene cluster containing eight core genes:[1][2] XdhD-YgfM or XdhAC: Uric acid reductase (yanthine formation) YgfK or UacX: Yanthine reductase SsnA: Amidohydrolase (ring cleavage) HyuA: Phenylhydantoinase YgeW or UacY: Carbamoyltransferase or D-aminoacylase YqeA: Carbamate kinase YgeY: Peptidase YgeX: Diaminopropionate ammonia lyase The complete pathway generates pyruvate, ammonia, and ATP, providing bacteria with carbon, nitrogen, and energy while reducing host uric acid burden.[1][2]
Distribution
The yanthine-mediated uric acid degradation pathway is widely distributed across phylogenetically diverse anaerobic gut bacteria:[1][2]
Pseudomonadota (Proteobacteria): Including E. coli and related Enterobacteriaceae Bacillota (Firmicutes): Including C. difficile, Clostridium sporogenes, Enterococcus faecalis, and Peptococcus prevotii Actinomycetota (Actinobacteria) Chloroflexota (Chloroflexi) Spirochaetota (Spirochaetes): Common in termite gut microbiomes Elusimicrobiota: Also prevalent in termite guts
The pathway has been identified in gut bacteria from humans, chickens, and termites. This widespread distribution suggests a host-microbe symbiosis where host-secreted uric acid creates a metabolic niche for bacteria capable of degrading it. In humans, approximately one-third of uric acid is excreted into the intestinal tract.[2]
Clinical significance
Detection in human serum
Yanthine has been detected in human plasma samples using liquid chromatography-mass spectrometry (LC-MRM-MS) with the optimized transition m/z 153.0→110.0. Key findings include:[1]
Yanthine is present at detectable levels in healthy individuals Serum yanthine levels are significantly elevated in gout patients compared to non-gout controls (P < 0.01) Higher yanthine concentrations correlate with higher uric acid levels Patients experiencing acute gout flares show the highest yanthine levels
Biomarker potential
The presence of yanthine in serum demonstrates gut-to-blood translocation of bacterial metabolites, indicating active intestinal uric acid catabolism. Yanthine may serve as a biomarker for gut bacterial uric acid metabolism activity, hyperuricemia risk assessment, and monitoring of gut microbiome metabolic function.[1]
Therapeutic applications
Understanding the yanthine pathway has led to development of engineered probiotics. CBT2.0 (CarBT4gout 2.0), an engineered E. coli Nissle 1917 derivative with constitutive overexpression of the uric acid degradation gene cluster, demonstrated in uricase-knockout hyperuricemic mice:[1]
Significant reduction in serum uric acid (171.63 vs 463.26 μmol/L, P < 0.001 at week 6) Decreased plasma creatinine (14.61 vs 34.14 μmol/L, P < 0.0001) Reduced kidney injury from uric acid crystals Sustained colonization detectable 8 weeks post-treatment Long-term uric acid reduction maintained
Detection methods
Yanthine can be detected using several analytical techniques:[1][2]
Fluorescence spectroscopy: Exploits yanthine's distinctive fluorescence (Ex: 308 nm, Em: 363 nm) LC-MS/MS: HILIC separation with MRM for quantification Stable isotope tracing: Using [¹³C₅]-labeled uric acid to track metabolic flux Co-elution with authentic standards: For definitive identification
Cofactor requirements
The formation and metabolism of yanthine involves multiple cofactors:[1][2]
Molybdenum cofactor (MoCo) FAD/FMN NAD(P)H Selenium (in Clostridium enzymes) Iron-sulfur clusters (4Fe-4S) Pyridoxal phosphate (PLP)
Pathway regulation
The uric acid degradation gene cluster is typically induced by uric acid or purine availability and repressed by preferred carbon sources (e.g., glucose) in wild-type bacteria. The pathway operates under anaerobic conditions due to oxygen-sensitive cofactors. Engineered strains employ constitutive and anaerobic-responsive promoters to overcome glucose repression.[1]
Pathway variants
Different bacterial lineages employ variations of the core pathway:[1][2]
Chloroflexota use a putative F420-dependent dehydrogenase instead of YgfK Some organisms use YgeW (carbamoyltransferase) while others use UacY (D-aminoacylase) Selenium-dependence of molybdenum hydroxylases varies across species
Comparison to other pathways
The yanthine pathway shares mechanistic similarities with the reductive pyrimidine degradation pathway, where YgfK-mediated yanthine reduction parallels PydA-mediated uracil reduction. An alternative anaerobic purine degradation route, the xanthinase pathway, is found in some Clostridia and Bacilli but has slower kinetics.[1][2]
History
While purine fermentation by Clostridium cylindrosporum was extensively studied in the 1950s by Rabinowitz and colleagues (describing the xanthinase pathway), the yanthine-mediated reductive pathway was only recently characterized in 2023-2025 by independent research groups:[1][2]
Liu et al. (2023) identified the gene cluster in Cell Kasahara et al. (2023) demonstrated the pathway's contribution to host purine homeostasis in Cell Host & Microbe Li et al. (2025) provided complete biochemical characterization of the E. coli pathway in Life Metabolism Liu et al. (2025) characterized the C. sporogenes pathway and identified selenium-dependent enzymes in Nature Microbiology
Nomenclature
The compound has been referred to as:[1][2]
2,8-Dioxopurine (systematic chemical name) Yanthine (biochemical name, by analogy to xanthine) UA-2 or DOP (intermediate designations in pathway studies)
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 Li, Zhi; Meng, Wei; Gao, Zihan; et al. (2025). "A reductive uric acid degradation pathway in anaerobic bacteria". Life Metabolism. 4 (6): loaf031. doi:10.1093/lifemeta/loaf031.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 Liu, Yuanyuan; Zhou, Zhiwei; Jarman, J. Bryce; et al. (2025). "Gut bacteria degrade purines via the 2,8-dioxopurine pathway". Nature Microbiology. 10: 2291–2305. doi:10.1038/s41564-025-02079-4.
External links
Full text of Li et al. (2025) in Life Metabolism Full text of Liu et al. (2025) in Nature Microbiology
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