Citraconic acid

Citraconate inhibits ACOD1 (IRG1) catalysis, reduces interferon responses and oxidative stress, and modulates inflammation and cell metabolism

Although the immunomodulatory and cytoprotective properties of itaconate have been studied extensively, it is not known whether its naturally occurring isomers mesaconate and citraconate have similar properties. Here, we show that itaconate is partially converted to mesaconate intracellularly and that mesaconate accumulation in macrophage activation depends on prior itaconate synthesis. When added to human cells in supraphysiological concentrations, all three isomers reduce lactate levels, whereas itaconate is the strongest succinate dehydrogenase (SDH) inhibitor. In cells infected with influenza A virus (IAV), all three isomers profoundly alter amino acid metabolism, modulate cytokine/chemokine release and reduce interferon signalling, oxidative stress and the release of viral particles. Of the three isomers, citraconate is the strongest electrophile and nuclear factor-erythroid 2-related factor 2 (NRF2) agonist. Only citraconate inhibits catalysis of itaconate by cis-aconitate decarboxylase (ACOD1), probably by competitive binding to the substrate-binding site. These results reveal mesaconate and citraconate as immunomodulatory, anti-oxidative and antiviral compounds, and citraconate as the first naturally occurring ACOD1 inhibitor.

Itaconate Isomers in Bread

The naturally occurring isomers itaconate, mesaconate and citraconate possess immunomodulatory, antioxidative and antimicrobial properties. However, it is not known whether they occur in commonly consumed human foods. Considering that they can arise as a result of heat conversion, we tested whether they occur in bread, representing a commonly consumed baked good. Using high-performance liquid chromatography-tandem mass spectrometry, we measured concentrations of the three isomers and their potential precursors, citrate and cis-aconitate, in unbaked sourdough and dough, and in crumb and crust of baked bread. All three isomers were detected at low concentrations (<20 pmol/mg dry weight) in sourdough, dough, crumb and crust. Concentrations of itaconate and citraconate were substantially higher in crust than in crumb of wheat and rye bread, and a modest increase in mesaconate was observed in crust of rye bread. In contrast, cis-aconitate concentrations were considerably lower in crust, which was consistent with the conversion of cis-aconitate to itaconate isomers due to higher temperature of the dough surface during baking. Based on data on the average consumption of bread and related baked goods in Germany, the daily intake of itaconate isomers was estimated to be roughly 7-20 ?g. Thus, baked goods constitute a regular dietary source of low amounts of itaconate isomers. In order to enable studies on the impact of dietary intake of itaconate isomers on human health, their concentrations should be assessed in other foods that are subjected to high heating.

pH-Responsive Charge-Conversion Progelator Peptides

A simple strategy for generating stimuli-responsive peptide-based hydrogels via charge-conversion of a self-assembling peptide (SAP) is described. These materials are formulated as soluble, polyanionic peptides, containing maleic acid, citraconic acid, or dimethylmaleic acid masking groups on each lysine residue, which do not form assemblies, but instead flow easily through high gauge needles and catheters. Acid-induced mask hydrolysis renews the zwitterionic nature of the peptides with concomitant and rapid self-assembly via β-sheet formation into rehealable hydrogels. The use of different masks enables one to tune pH responsiveness and assembly kinetics. In anticipation of their potential for in vivo hydrogel delivery and use, progelators exhibit hemocompatibility in whole human blood, and their peptide components are shown to be noncytotoxic. Finally, demonstration of stimuli-induced self-assembly for dye sequestration suggests a simple, non-covalent strategy for small molecule encapsulation in a degradable scaffold. In summary, this simple, scalable masking strategy allows for preparation of responsive, dynamic self-assembling biomaterials. This work sets the stage for implementing biodegradable therapeutic hydrogels that assemble in response to physiological, disease-relevant states of acidosis.

Improvement of dicarboxylic acid production with Methylorubrum extorquens by reduction of product reuptake

The methylotrophic bacterium Methylorubrum extorquens AM1 has the potential to become a platform organism for methanol-driven biotechnology. Its ethylmalonyl-CoA pathway (EMCP) is essential during growth on C1 compounds and harbors several CoA-activated dicarboxylic acids. Those acids could serve as precursor molecules for various polymers. In the past, two dicarboxylic acid products, namely mesaconic acid and 2-methylsuccinic acid, were successfully produced with heterologous thioesterase YciA from Escherichia coli, but the yield was reduced by product reuptake. In our study, we conducted extensive research on the uptake mechanism of those dicarboxylic acid products. By using 2,2-difluorosuccinic acid as a selection agent, we isolated a dicarboxylic acid import mutant. Analysis of the genome of this strain revealed a deletion in gene dctA2, which probably encodes an acid transporter. By testing additional single, double, and triple deletions, we were able to rule out the involvement of the two other DctA transporter homologs and the ketoglutarate transporter KgtP. Uptake of 2-methylsuccinic acid was significantly reduced in dctA2 mutants, while the uptake of mesaconic acid was completely prevented. Moreover, we demonstrated M. extorquens-based synthesis of citramalic acid and a further 1.4-fold increase in product yield using a transport-deficient strain. This work represents an important step towards the development of robust M. extorquens AM1 production strains for dicarboxylic acids. KEY POINTS: ? 2,2-Difluorosuccinic acid is used to select for dicarboxylic acid uptake mutations. ? Deletion of dctA2 leads to reduction of dicarboxylic acid uptake. ? Transporter-deficient strains show improved production of citramalic acid.

The reaction of 1-vinylnaphthalene and 6-methoxy-1-vinylnaphthalene with citraconic anhydride, fumaric acid and mesaconic acid