The biocatalytic production of flavor naturals that determine chemosensory percepts of foods and beverages is an ever challenging target for academic and industrial research. Advances in chemical trace analysis and post-genomic progress at the chemistry-biology interface revealed odor qualities of nature's chemosensory entities to be defined by odorant-induced olfactory receptor activity patterns. Beyond traditional views, this review and meta-analysis now shows characteristic ratios of only about 3 to 40 genuine key odorants for each food, from a group of about 230 out of circa 10 000 food volatiles. This suggests the foodborn stimulus space has co-evolved with, and roughly match our circa 400 olfactory receptors as best natural agonists. This perspective gives insight into nature's chemical signatures of smell, provides the chemical odor codes of more than 220 food samples, and beyond addresses industrial implications for producing recombinants that fully reconstruct the natural odor signatures for use in flavors and fragrances, fully immersive interactive virtual environments, or humanoid bioelectronic noses.

Plants are indispensable for life on earth and represent organisms of extreme biological diversity with unique molecular capabilities 1. Here, we present a quantitative atlas of the transcriptomes, proteomes and phosphoproteomes of 30 tissues of the model plant Arabidopsis thaliana. It provides initial answers to how many genes exist as proteins (>18,000), where they are expressed, in which approximate quantities (>6 orders of magnitude dynamic range) and to what extent they are phosphorylated (>43,000 sites). We present examples for how the data may be used, for instance, to discover proteins translated from short open reading frames, to uncover sequence motifs involved in protein expression regulation, to identify tissue-specific protein complexes or phosphorylation-mediated signaling events to name a few. Interactive access to this unique resource for the plant community is provided via ProteomicsDB and ATHENA which include powerful bioinformatics tools to explore and characterize Arabidopsis proteins, their modifications and interplay. Main The plant model organism Arabidopsis thaliana (AT) has revolutionized our understanding of plant biology and influenced many other areas of the life sciences 1. Knowledge derived from Arabidopsis has also provided mechanistic understanding of important agronomic traits in crop species 2. The Arabidopsis genome was sequenced 20 years ago and hundreds of natural variants have since been analyzed at the genome and epigenome level 3,4. In contrast, the Arabidopsis proteome as the main executer of most biological processes is far less comprehensively characterized. To address this gap, we used state-of-the-art mass spectrometry and RNA sequencing (RNA-seq) to provide the first integrated proteomic, phosphoproteomic and transcriptomic atlas of Arabidopsis. Illustrated by selected examples, we show how this rich molecular resource can be used to explore the function of single proteins or entire pathways across multiple omics levels. Multi-omics atlas of Arabidopsis We generated an expression atlas covering, on average, 17,603 ± 1,317 transcripts, 14,430 ± 911 proteins and 14,689 ± 2,509 phosphorylation sites (p-sites) per tissue, using a reproducible biochemical and analytical approach (Fig. 1a,b; Extended Data Fig. 1a-c; Supplementary Data 1,2). In total, the protein expression data covers 18,210 of the 27,655 protein-coding genes (66%) annotated in Araport11 5. This is a substantial increase compared to the percentage of genes with protein level evidence reported in UniProt (27%) 6 and more than double the number of proteins identified in an earlier tissue proteome analysis 7 (Fig. 1c, Extended Data Fig. 1d-f). In addition, we report tissue-resolved quantitative evidence for a total of 43,903 p-sites making this study the most comprehensive single Arabidopsis phosphoproteome published to date (Fig. 1c). 47% of the expressed proteome was found to be phosphorylated in at least one instance, confirming earlier analyses of individual

Comparative sensory analysis revealed that a 44-week-matured Gouda cheese (GC44) exhibited a much more pronounced mouthfulness and long-lasting taste complexity when compared to a young Gouda cheese ripened for only 4 weeks (GC4). To identify the molecules underlying that so-called kokumi sensation, a sensomics approach was applied on the water-soluble extract (WSE44) of GC44 by combining gel permeation chromatography (GPC) with analytical sensory tools. HPLC-MS/MS experiments on GPC fractions inducing a kokumi sensation when tasted in an aqueous biomimetic taste recombinant solution (rWSE44) enabled the identification of 8 alpha-L-glutamyl and 10 gamma-L-glutamyl dipeptides as candidate kokumi-enhancing molecules. Among those, only the gamma-L-glutamyl dipeptides were found to impart an enhanced kokumi sensation to the matured cheese, whereas none of the alpha-glutamyl peptides were found to be active. Among the gamma-L-glutamyl peptides, the candidates gamma-Glu-Glu, gamma-Glu-Gly, gamma-Glu-Gln, gamma-Glu-Met, gamma-Glu-Leu, and gamma-Glu-His, present in GC44 in concentrations between 4.11 and 17.66 micromol/kg, were identified for the first time as the key kokumi molecules enhancing mouthfulness and complex taste continuity of the matured cheese.

Addition of a nearly tasteless aqueous extract isolated from beans (Phaseolus vulgaris L.) to a model chicken broth enhanced its mouthfulness and complexity and induced a much more long-lasting savory taste sensation on the tongue. Gel permeation chromatography and hydrophilic interaction liquid chromatography/comparative taste dilution analysis (HILIC/cTDA), followed by LC-MS/MS and 1D/2D-NMR experiments, led to the identification of gamma-L-glutamyl-L-leucine, gamma-L-glutamyl-L-valine, and gamma-L-glutamyl-L-cysteinyl-beta-alanine as key molecules inducing this taste-modifying effect. Sensory analysis of aqueous solutions of these peptides showed threshold concentrations between 3.3 and 9.4 mmol/L for an unspecific, slightly astringent sensation. More interestingly, when added to a savory matrix such as sodium chloride and monosodium glutamate solutions or chicken broth, the detection thresholds of these gamma-glutamyl peptides decreased significantly and remarkably enhanced mouthfulness, complexity, and long-lastingness of the savory taste were observed; for example, the threshold of gamma-glutamyl-cysteinyl-beta-alanine decreased by a factor of 32 in a binary mixture of glutamic acid and sodium chloride. As tasteless molecules inducing mouthfulness, thickness, and increasing continuity of savory foods were coined about 10 years ago as "kokumi" flavor compounds, the peptides identified in raw as well as thermally treated beans have to be considered as kokumi compounds.

Sensory-directed fractionation of a double-boiled chicken broth using ultrafiltration, gel permeation chromatography, PFPP-HPLC, and HILIC combined with analytical sensory techniques led to the identification of beta-alanyl-N-methyl-l-histidine, beta-alanyl-l-histidine, and the previously unreported beta-alanylglycine as the key contributors to the thick-sour orosensation and typical white-meaty character of chicken broth. Quantitative analysis, followed by taste recombination and omission experiments, revealed for the first time that, when present together with l-glutamic acid and sodium and/or potassium ions, subthreshold concentrations of these beta-alanyl peptides enhance the typical thick-sour orosensation and white-meaty character known for poultry meat, although these taste-modulatory peptides exhibited only a faint sour and slightly astringent intrinsic taste when tasted individually.

BackgroundAs the gut microbiota contributes to metabolic health, it is important to determine specific diet-microbiota interactions that influence host metabolism. Bile acids and dietary fat source can alter phenotypes of diet-induced obesity, but the interplay with intestinal microorganisms is unclear. Here, we investigated metabolic consequences of diets enriched in primary bile acids with or without addition of lard or palm oil, and studied gut microbiota structure and functions in mice.ResultsIn combination with bile acids, dietary lard fed to male C57BL/6N mice for a period of 8 weeks enhanced fat mass accumulation in colonized, but not in germ-free mice when compared to palm oil. This was associated with impaired glucose tolerance, lower fasting insulin levels, lower counts of enteroendocrine cells, fatty liver, and elevated amounts of hepatic triglycerides, cholesteryl esters, and monounsaturated fatty acids. Lard- and bile acid-fed mice were characterized by shifts in dominant gut bacterial communities, including decreased relative abundances of Lachnospiraceae and increased occurrence of Desulfovibrionaceae and the species Clostridium lactatifermentans and Flintibacter butyricus. Metatranscriptomic analysis revealed shifts in microbial functions, including lipid and amino acid metabolism.ConclusionsCaution is required when interpreting data from diet-induced obesity models due to varying effects of dietary fat source. Detrimental metabolic consequences of a diet enriched with lard and primary bile acids were dependent on microbial colonization of the host and were linked to hepatic lipid rearrangements and to alterations of dominant bacterial communities in the cecum.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0510-8) contains supplementary material, which is available to authorized users.

Regulatory myeloid immune cells, such as myeloid-derived suppressor cells (MDSCs), populate inflamed or cancer tissue and block immune cell effector functions. Lack of mechanistic insight 54 into MDSC suppressive activity and a marker for their identification hampered attempts to 55 overcome T cell-inhibition and unleash anti-cancer immunity. Here we report that human MDSCs 56 were characterized by strongly reduced metabolism and conferred this compromised metabolic 57 state to CD8 + T cells thereby paralyzing their effector functions. We identified accumulation of the dicarbonyl-radical methylglyoxal, generated by semicarbazide-sensitive amine oxidase (SSAO), to cause the metabolic phenotype of MDSCs and MDSC-mediated paralysis of CD8 + T cells. In a murine cancer model, neutralization of dicarbonyl-activity overcame MDSC-mediated T cell-suppression and together with checkpoint inhibition improved efficacy of cancer immune therapy. Our results identify the dicarbonyl methylglyoxal as marker metabolite for MDSCs that mediates T cell paralysis and can serve as target to improve cancer immune therapy. Results 92 Dormant metabolic phenotype in MDSCs 93Suppressive myeloid cells arise during chronic inflammation in tissues 17 , and tissue stromal cells 94 induce transition of monocytes into monocytic MDSCs 16 . We exploited this capacity of stromal cells to convert human peripheral blood monocytes into MDSCs, which are phenotypically similar 96 to CD14 + HLA-DR -/low suppressive myeloid cells directly isolated from cancer patients 16 , to characterize the mechanism of MDSC-mediated T cell suppression. Transcriptome analysis showed less than 200 differentially expressed genes between MDSCs and monocytes, which did not include surface molecules suitable for phenotypic discrimination or known immune suppressive mediators to explain their suppressive activity (supplementary table I-IV, Extended Data Fig. 1). Consistently, blockade of known immune suppressive mediators did not prevent MDSC-mediated T cell suppression (Extended Data Fig. 2). Surprisingly, we found downregulation of genes encoding glycolysis-related enzymes in MDSCs (Fig. 1a, and Extended Data Table V).Indeed, MDSCs showed reduced glucose uptake and Glut1 surface expression (Fig. 1b), the main transporter mediating glucose uptake in immune cells. As predicted from gene expression analysis, hexokinase activity was lower in MDSCs (Fig. 1c). To validate these results, we isolated CD14 + HLA-DR -/lo cells from tumor tissue of patients with hepatocellular carcinoma by enzymatic digestion followed by density centrifugation and flow cytometric cell sorting. We confirmed reduced glucose uptake and hexokinase activity in CD14 + HLA-DR -/low cells isolated from tumor tissue of cancer patients (Fig. 1d,e, and Extended Data Table VI), which are considered to represent MDSCs. Strikingly, MDSCs failed to utilize glucose for glycolysis and also showed reduced cellular bioenergetics, i.e. lower mitochondrial membrane potential quantified by the potentiometric mitochondrial ...

As enzymatic digests of fish proteins were recently reported to enhance salt taste, the fish protein protamine was digested by chymotrypsin and trypsin and subsequently screened for candidate salt taste modulating (STM) peptides. To achieve this, first, a two-step sensory assay was developed and demonstrated to be a rather suitable tool for the detection of salt taste enhancers and the "quantitation" of their salt taste enhancing activity on the basis of isointensities with reference solutions. By means of activity-guided fractionation using ultrafiltration, gel permeation chromatography, and hydrophilic liquid interaction chromatography in combination with the sensory assay for STM activity assessment, a series of arginyl dipeptides, with RP, RA, AR, RG, RS, RV, VR, and RM being the most active, as well as l-arginine were found as salt taste enhancing molecules in fish protamine digests. For the first time, HPLC-MS/MS analysis on a PFP and a HILIC stationary phase, respectively, enabled the quantitative analysis of the arginyl peptides in a series of commercial and laboratory-made protein hydrolysates as well as fermented fish sauces.