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PubMed2005

Structures, sensory activity, and dose/response functions of 2,5-diketopiperazines in roasted cocoa nibs (Theobroma cacao).

The taste compounds inducing the blood-like, metallic bitter taste sensation reported recently for a dichloromethane extract prepared from roasted cocoa nibs were identified as a series of 25 diketopiperazines by means of HPLC degustation, LC-MS/MS, and independent synthesis. Among these 25 compounds, 13 cis-configured diketopiperazines, namely, cyclo(L-IIe-L-Phe), cyclo(L-Val-L-Leu), cyclo(L-Pro-L-Pro), cyclo(L-IIe-L-Pro), cyclo(L-Val-L-Tyr), cyclo(L-Ala-L-Tyr), cyclo(L-Phe-L-Ser), cyclo(L-Ala-L-IIe), cyclo(L-Leu-L-Phe), cyclo(L-Pro-L-Val), cyclo(L-Pro-L-Thr), cyclo(L-Pro-L-Tyr), and cyclo(L-Val-L-Val) were identified for the first time in cocoa. In addition, the taste recognition thresholds for the metallic as well as the bitter taste of the diketopiperazines were determined, and after quantitative analysis by using two diastereomeric diketopiperazines as the internal standards, the sensory impact of the diketopiperazines was evaluated on the basis of their dose-over-threshold (DoT) factors calculated as the ratio of the concentration and the threshold concentration of a compound. These data revealed DoT factors above 1.0 exclusively for cis-cyclo(L-Pro-L-Val), cis-cyclo(L-Val-L-Leu), cis-cyclo(L-Ala-L-Ile), cis-cyclo(L-Ala-L-Leu), and cis-cyclo(L-Ile-L-Pro), whereas all of the other diketopiperazines were present below their individual bitter taste threshold concentrations and should therefore not contribute to the cocoa taste. Because the DoT factors do not consider the nonlinear relationship between the concentration and gustatory response of an individual compound, we, for the first time, report on the recording of dose/response functions describing the human bitter taste perception of diketopiperazines more precisely.

Adult↗
PubMed2000

Taste active compounds in a goat cheese water-soluble extract. 2. Determination of the relative impact of water-soluble extract components on its taste using omission tests.

The aim of this work was to determine the relative impact of water-soluble compounds on the gustatory properties of a goat cheese water-soluble extract (WSE). Using a semisynthetic model mixture (MWSE) previously elaborated in physicochemical and gustatory accordance with the cheese WSE (see part 1, Engel et al. J. Agric. Food Chem. 2000, 48, 4252-4259), omission tests were performed. Among the main taste characteristics of the WSE (salty, sour, and bitter), saltiness was explained by an additive contribution of sodium, potassium, calcium, and magnesium cations, whereas sourness was mainly due to a synergistic effect involving sodium chloride, phosphates, and lactic acid and bitterness was found to result from calcium and magnesium chlorides, the impact of which was partially masked by sodium chloride. In contrast, amino acids, lactose, and peptides did not have any significant impact on WSE taste properties. To quantify the contribution of the taste active compounds to bitterness and saltiness, stepwise multiple linear regressions were performed. Those contributions were expressed as a percentage of the considered taste characteristic intensity in the WSE. The model obtained allowed up to 97.4% of the perceived saltiness to be described and approximately 85% of the bitterness.

Animals↗
PubMed1985

Diterpenoid sweeteners. Synthesis and sensory evaluation of stevioside analogues with improved organoleptic properties.

Congeneric series of stevioside (1) and rebaudioside A (3) analogues have been prepared. It was found that the bitter-taste component endogenous in the natural compounds 1 and 3 may be eliminated by increase in molecular hydrophilic character. Through the series of compounds prepared, bitter-taste character was correlated with k', a chromatographic indicator of gross hydrophilicity. An analogue (11) of stevioside, shown chromatographically to be of increased hydrophilicity, was prepared and found to exhibit no bitter-taste character. Similarly an analogue (13) of rebaudioside A, having increased polarity, was prepared and found not to exhibit any bitter taste. The rebaudioside A analogue 13 was determined to have higher potency than 11 is suggested as a potential non-nutritive sweetener for food applications.

Diterpenes↗
PubMed2004

Detection and recognition thresholds to the 4 basic tastes in Mexican patients with primary Sjögren's syndrome.

BACKGROUND: Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease characterized by inflammatory lymphocytic infiltration of the salivary glands, leading to dryness of the mouth (xerostomia). It has been postulated that xerostomia is the preceding stage for the development of alterations in taste acuity (dysgeusia) in this type of patients. OBJECTIVES: To determine detection and recognition thresholds to the 4 basic tastes (sweet, salty, sour and bitter) in pSS patients and compare them to a control group. To determine if the long-term consumption of chile peppers and spicy Mexican diets had an effect on the taste perception and acuity of the pSS patients. SETTING: This study was done in the Department of Food Science and Technology of the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNSZ), a third-level hospital in Mexico City. SUBJECTS: The patient group consisted of 21 Mexican females (mean +/- s.d., age: 53.1 +/- 9.8 y) diagnosed with pSS (time of duration of the disease, 8.6 +/- 6.6 y, median 7 y, range 1-25 y) who were recruited at the outpatient service of the Department of Immunology and Rheumatology of the INCMNSZ. The control group consisted of 20 healthy nonsmokers age-matched Mexican women (50.3 +/- 11.9 y) most of them personnel of the INCMNSZ, and some friends and nonblood relatives to the patients (sisters-in-law) who volunteered to participate in the study. INTERVENTIONS: Detection and recognition thresholds were determined by the method of least noticeable differences on three occasions during three nonconsecutive days. Saliva production was determined by Saxon's test on two separate occasions. RESULTS: Although saliva production was severely reduced in pSS patients (1.35 +/- 0.55 ml/2 min, P<0.001) compared to controls (6.26 +/- 2.41 ml/2 min), all subjects recognized the 4 basic tastes when these were tested at suprathreshold concentrations. The detection thresholds for the sweet, sour and bitter tastes were higher in pSS patients, as well as the recognition thresholds for the salty, sour and bitter tastes. A relationship between time of evolution of the disease and saliva production with individual thresholds could not be established. CONCLUSIONS: pSS patients exhibited different degrees of dysgeusia depending on the taste being studied, that is, they were mildly dysgeusic for the sweet and salty tastes and clearly dysgeusic for the sour and bitter tastes. Although both pSS patients and controls had consumed 'typical Mexican diets' their entire lives, our results showed that the consumption of chile peppers and spicy foods did not have any effect on the taste perception and acuity of the pSS patients.

Capsicum↗
PubMed2001

[A plant extract and its modified preparation in functional dyspepsia. Results of a double-blind placebo controlled comparative study].

AIMS: To assess the efficacy and safety of the commercially available herbal preparation (Iberogast, STW-5*) containing extracts from bitter candy tuft, chamomile flower, peppermint leaves, caraway fruit, licorice root, lemon balm leaves, angelica root, celandine herbs, milk thistle fruit and its research preparation STW-5-S (without bitter candy tuft) in patients with functional dyspepsia. PATIENTS AND METHODS: After a standardized diagnostic work-up and at least 7 days free of medication, 60 patients, diagnosed with functional dyspepsia, were recruited in a multicenter trial and randomly assigned to one of 3 treatment groups (STW-5, STW-5-S or placebo). Each patient received the treatment for 4 weeks. The main outcome variables were the improvement of a gastrointestinal symptom score (GIS), a sumscore consisted of 10 dyspeptic symptoms rated on a Likert scale. Dyspeptic symptoms were assessed at baseline, 2 and 4 weeks after treatment. RESULTS: 60 patients completed the trial (mean age 46.8 years, range 25-70, female 38 patients). Compared with placebo-group both herbal preparations STW-5 and STW-5-S showed a clinically significant improvement of GIS after 2 and 4 weeks of treatment (p < 0.001). No statistically significant difference could be observed between the efficacy of STW-5 and STW-5 S (p > 0.05), but a solid improvement of gastrointestinal symptoms could be achieved earlier with STW-5 than with its research preparation STW-5-S without bitter candy tuft (p = 0.023). CONCLUSIONS: In patients with functional dyspepsia, the commercially available herbal preparation STW-5 and its modified dispense STW-5-S tested improved dyspeptic symptoms significantly better than placebo. The extract bitter candy tuft appeared to have an additive effect on dyspeptic symptoms.

Adult↗
PubMed1994

High alpha-tomatine content in ripe fruit of Andean Lycopersicon esculentum var. cerasiforme: developmental and genetic aspects.

A variant of Lycopersion esculentum var. cerasiforme is described that deviates from the typical form of the entire species, including cultivated tomatoes, in possessing high levels (500-5000 micrograms/g of dry weight) of the steroidal alkaloid alpha-tomatine in its ripe fruits. This biotype is restricted to a tiny enclave in the valley of Río Mayo, Department San Martín, Peru. Among 88 accessions of var. cerasiforme from its present distribution in the Andes, a 90% association was found between high tomatine and bitter flavor; within the Mayo watershed, all samples from the upper drainage had bitterness and high tomatine; the frequency of both traits decreased to low levels toward the lower end. Tomatine therefore probably is the source of bitterness. Throughout L. esculentum tomatine is present at very high concentrations in earliest stages of fruit development, thereafter decreasing rapidly to midperiod, and finally diminishing gradually to near zero at maturity as a result of catabolism to biologically inert compounds, except in the variant described here. High tomatine content does not appear to affect adversely either the natives, among whom the bitter types are popular, or individuals who sampled them in this survey. Genetic determination of high tomatine in ripe fruits is totally recessive and appears to be monogenic with interaction with genes of minor effect. The prevailing pattern of glycoalkaloid synthesis and degradation in development of solanaceous fruits suggests a mechanism to protect against predation prior to ripening but to permit it afterward as a device to promote dispersal. In consideration of the nondegradative nature of the variant, its genetic determination, and very restricted geographic distribution, mutation to this form appears to be a random event of doubtful evolutionary significance.

Chromatography, Gas↗
PubMed1997

Sensory acceptance of Japanese green tea and soy products is linked to genetic sensitivity to 6-n-propylthiouracil.

Genetic sensitivity to 6-n-propylthiouracil (PROP), a heritable trait, has been linked to increased sensitivity to and increased dislike of other bitter compounds. Many phytochemicals with reputed chemopreventive activity have a bitter taste. This study tested the hypothesis that PROP-sensitive women would be more likely to reject Japanese green tea and selected soy products. Both foods contain bitter flavonoids that are thought to be useful in cancer prevention and control. Study subjects, 53 normal-weight, healthy young women, were divided into PROP nontasters (n = 14), regular tasters (n = 28), and supertasters (n = 11) on the basis of their PROP detection thresholds and mean response ratios to PROP compared with NaCl solutions. The subjects tasted a range of soy products, including tofu, miso, plain soymilk, vanilla-flavored soymilk, and five different concentrations of Japanese green tea. Taste intensity and hedonic preference ratings were measured using nine-point category scales. PROP sensitivity was linked to greater perceived bitterness and increased dislike of Japanese green tea. PROP tasters and supertasters preferred vanilla-flavored soymilk over other soy products. Genetic taste markers may alter dietary exposure to substances thought to affect cancer risk.

Adult↗
PubMed1976

Structural relationships of sugars to taste.

Chemical modification of sugars and their simple analogues indicates that these types of compound are almost always sweet, bitter, or bitter/sweet; hence, the two basic tastes may be intimately associated features of the same molecule. Stepwise modification at each chiral center around the sugar ring allows the sapid functions in these molecules to be mapped and leads to the inescapable conclusion that sugar molecules may be "polarized" on taste bud receptors, so that one end of the molecule elicits sweetness and the other bitterness. However, more extensive chemical modification evidently causes the molecule to realign itself in entirely different ways on the receptor. In most oligosaccharides only one sugar residue is likely to bind to the taste receptor, and this is probably a nonreducing end group, because the anomeric center of glucopyranose types of structure does not appear to affect sweetness. Sweetness depresses bitterness and bitterness depresses sweetness. Hence, it is not possible to make structural comparisons between analogues without correcting for these effects. However, some semiquantitative studies have established the value of current hydrogen bond theories of sweetness and the ideal oxygen-oxygen interorbital spacings for sweetness criteria in sugar molecules.

Acetates↗
PubMed2003

Peptides from milk proteins and their properties.

This review has attempted to study the literature pertaining to peptides derived from milk proteins. Hydrolysis of milk proteins to generate peptides has been practiced for a long time and it was recognized early on in this process that the taste of hydrolyzates might hinder use of these products in food formulations. Modification of protein is necessary to form a more acceptable or utilizable product, to form a product that is less susceptible to deteriorative reactions and to form a product that is of higher nutritionall quality. Modifications may be achieved by a number of chemical and enzymatic means. This review has considered only enzymatic modification of dairy proteins. Modified proteins contain peptides and some of these peptides have been purified and their functionalities have been compared with unmodified proteins. This paper has examined the literature pertaining to improvement in functionality of enzyme-modified proteins. Improvements in solubility, emulsification, foaming and gelation were examined. There is limited information available on the sequence of the peptides necessary to improve the functional characteristics of proteins. Knowing the sequences of desirable functional peptides can lead to genetic alteration of proteins to improve functionality. Addition of synthetic peptides to intact proteins may be another way in which the functionality of proteins can be augmented. Some of the peptides in milk proteins are capable of affecting biological functions of an organism. These effects can be antimicrobial and probiotic, i.e., prevent the growth and proliferation of undesirable and pathogenic organisms, or they may promote the growth of desirable bacteria in the digestive tract of humans and animals. Peptides derived from milk protein have been shown to exert digestive and metabolic effects as well. They may also influence the immune system. These biological effects may play an important role in the development of medical foods that treat or mitigate the effects of diseases. Proteins are allergens and therefore it is possible that products derived from modification of proteins may also be allergens. The known literature about the allergenicity of peptides derived from milk proteins has been examined in this article. Last, but not the least, the taste attributes of peptides is also considered. Bitterness of hydrolyzates is a common occurrence and the origins of these bitter peptides and possible ways of mitigating this sensory defect has been discussed. Many of the peptides that enhance functionality and exert biological activity are likely to be bitter. Therefore, the bitter taste of hydrolysis products has to be dealt with in boosting the functional or nutraceutical aspects of foods containing these peptides. Analytical techniques for sequencing peptides have become more accessible and purification of peptides is commercially feasible. Computer based modeling techniques have aided the prediction of structures in these peptides. These advances, coupled with the advances in biotechnology, promise to revolutionize the future of nutraceutical and functional foods.

Animals↗
PubMed1996

Some basic psychophysics of calcium salt solutions.

Detection thresholds and the taste qualities of suprathreshold concentrations of calcium salt solutions were assessed. Average taste detection thresholds for calcium chloride (CaCl2), lactate (CaLa), hydroxide, phosphate and gluconate ranged between 8 and 50 mM, with no reliable differences among the various salts. Between-subject variability ranged over four orders of magnitude and reliability coefficients for repeated detection threshold tests of CaCl2 averaged r = 0.52. In an odor detection test, subjects could reliably discriminate 100 but not 1 mM CaCl2 and CaLa from water. The taste of suprathreshold concentrations (1-100 mM) of CaCl2 and CaLa was considered unpleasant. At 1 mM, CaCl2 solution was rated as 35% bitter, 32% sour, 29% sweet and 4% salty. At higher concentrations the sweet component diminished and the salty component increased, so that 100 mM CaCl2 was rated as 44% bitter, 20% sour, 1% sweet and 35% salty. CaLa solutions were considered to be significantly less bitter and marginally more sour than equimolar CaCl2 solutions. Thus, the taste of calcium varied with both the form and concentration of salt tested, but included both sour and bitter components. Saltiness was identified only in high (> or = 32 mM) concentrations of CaCl2, and thus was not necessarily a component of calcium taste.

Adult↗
PubMed2000

Autonomic nervous system responses associated with primary tastes.

The hedonic dimension of the taste sensation plays a crucial role in the control of many taste-mediated responses related to food ingestion or rejection. The purpose of this study was to evaluate the emotional reactivity associated with each primary taste (sweet, salty, sour and bitter) through analysis of the variations of autonomic nervous system (ANS) parameters. Thirty-four healthy non-smoker volunteer subjects (17 males and 17 females, mean age = 28 years) participated in the experiment. Taste stimuli were solutions of 0.3 M sucrose (sweet), 0.15 M NaCl (salty), 0.02 M citric acid (sour) and 0.00015 M quinine sulfate (bitter). Evian mineral water was used as the diluent and control (neutral taste). Throughout the test, five ANS parameters (skin potential and skin resistance, skin blood flow and skin temperature, and instantaneous heart rate) were simultaneously and continuously recorded. Results of the ANOVA evidenced a significant effect of primary taste on skin resistance amplitude (P: < 0.001) and duration (P: < 0.0001), skin temperature amplitude (P: < 0.001), skin blood flow amplitude (vasoconstriction) (P: < 0.0001) and instantaneous heart rate increase (P: < 0.0001). Skin resistance and cardiac responses were the most relevant ANS parameters to distinguish among the taste solutions. The four primary tastes could be associated with significantly different ANS responses in relation to their hedonic valence: the pleasantly connoted and innate-accepted sweet taste induced the weakest ANS responses whereas the unpleasant connoted tastes (salty, sour and bitter) induced stronger ANS responses, the innate-rejected bitter taste inducing the strongest ones. Such a neurovegetative characterization of each primary taste could provide references for the hedonic analysis of the more complex gustative sensation attached to foods.

Adult↗
PubMed2001

PROP (6-n-Propylthiouracil) tasting and sensory responses to caffeine,sucrose, neohesperidin dihydrochalcone and chocolate.

The genetically determined ability to taste 6-n-propylthiouracil (PROP) has been linked with lowered acceptance of some bitter foods. Fifty-four women, aged 18-30 years, tasted and rated PROP-impregnated filter paper and seven solutions of PROP. Summed bitterness intensity ratings for PROP solutions determined PROP taster status. Respondents also tasted five sucrose and seven caffeine solutions, as well as seven solutions each of caffeine and PROP that had been sweetened with 0.3 mmol/l neohesperidin dihydrochalcone (NHDC). Respondents also rated three kinds of chocolate using 9-point category scales. PROP tasters rated caffeine solutions as more bitter than did non-tasters and liked them less. PROP tasters did not rate either sucrose or NHDC as more sweet. The addition of NHDC to PROP and caffeine solutions suppressed bitterness intensity more effectively for tasters than for non-tasters and improved hedonic ratings among both groups. PROP tasters and non-tasters showed the same hedonic response to sweetened caffeine solutions and did not differ in their sensory responses to chocolate. Genetic taste markers may have only a minor impact on the consumption of such foods as sweetened coffee or chocolate.

Adolescent↗
PubMed2001

Genetic taste responses to 6-n-propylthiouracil among adults: a screening tool for epidemiological studies.

Genetically mediated taste responsiveness to 6-n-propylthiouracil (PROP) has been linked to reduced acceptance of some bitter foods. In this community-based study male (n = 364) and female (n = 378) adults enrolled in a self-help dietary intervention trial were screened for PROP taster status. Respondents, aged 18--70 years, were mailed filter papers impregnated with PROP or with aspartame solutions. They received instructions to rate taste intensity and hedonic preference using nine point category scales. Women rated PROP as more bitter than did men. Both sweetness and bitterness ratings were lower for older adults. Taste responsiveness to PROP was unrelated to body mass index in women or men. Higher bitterness ratings for PROP were weakly associated with higher sweetness ratings for aspartame, but were unrelated to sweet taste preferences. Successful administration of PROP filter papers by mail suggests new avenues for the screening of taste phenotypes in epidemiological studies.

Adolescent↗
PubMed2001

Binary taste mixture interactions in prop non-tasters, medium-tasters and super-tasters.

It is generally assumed that the mutual, but asymmetric, suppression of the components in binary taste mixtures is an invariant property of the human psychophysical response to such mixtures. However, taste intensities have been shown to vary as a function of individual differences in sensitivity, indexed by the perceived bitterness of 6-n-propylthiouracil (PROP). To determine if these variations in taste perception influence taste mixture interactions, groups of PROP super-, medium- and non-tasters assessed four binary taste mixtures: sweet-bitter [sucrose/quinine hydrochloride (QHCl)], sweet-sour (sucrose/citric acid), salty-bitter (NaCl/QHCl) and salty-sour (NaCl/citric acid). In each experiment, subjects received factorial combinations of four levels of each of two tastants and rated individual taste intensities and overall mixture intensity. For each taste quality, super-tasters typically gave higher ratings than either medium- or non-tasters, who tended not to differ. There were also group differences in the interactions of the mixtures' components. Super-tasters rated the overall intensity of the mixtures, most likely reflecting integration of the taste components, as greater than medium- and non-tasters, who again showed few differences. In sweet-bitter mixtures, non-tasters failed to show the suppression of sweetness intensity by the highest QHCl concentration that was evident in super- and medium-tasters. These data show that the perception of both tastes and binary taste mixture interactions varies as a function of PROP taster status, but that this may only be evident when three taster groups are clearly distinguished from one another.

Adolescent↗
PubMed2004

RGS21 is a novel regulator of G protein signalling selectively expressed in subpopulations of taste bud cells.

Abstract G-protein-mediated signalling processes are involved in sweet and bitter taste transduction. In particular, the G protein alpha-subunit gustducin has been implicated in these processes. One of the limiting factors for the time-course of cellular responses induced by tastants is therefore the intrinsic GTPase activity of alpha-gustducin, which determines the lifetime of the active G protein complex. In several signalling systems specific 'regulator of G protein signalling' (RGS) proteins accelerate the GTPase activity of G protein alpha-subunits. Using differential screening approaches, we have identified a novel RGS protein termed RGS21, which represents the smallest known member of this protein family. Reverse transcription polymerase chain reaction and in situ hybridization experiments demonstrated that RGS21 is expressed selectively in taste tissue where it is found in a subpopulation of sensory cells. Furthermore, it is coexpressed in individual taste cells with bitter and sweet transduction components including alpha-gustducin, phospholipase Cbeta2, T1R2/T1R3 sweet taste receptors and T2R bitter taste receptors. In vitro binding assays demonstrate that RGS21 binds alpha-gustducin in a conformation-dependent manner and has the potential to interact with the same Galpha subtypes as T1R receptors. These results suggest that RGS21 could play a regulatory role in bitter as well as sweet taste transduction processes.

Aluminum Compounds↗
PubMed2003

Evolutionary relationships of the Tas2r receptor gene families in mouse and human.

The early molecular events in the perception of bitter taste start with the binding of specific water-soluble molecules to G protein-coupled receptors (GPCRs) encoded by the Tas2r family of taste receptor genes. The identification of the complete TAS2R receptor family repertoire in mouse and a comparative study of the Tas2r gene families in mouse and human might help to better understand bitter taste perception. We have identified, cloned, and characterized 13 new mouse Tas2r sequences, 9 of which encode putative functional bitter taste receptors. The encoded proteins are between 293 and 333 amino acids long and share between 18% and 54% sequence identity with other mouse TAS2R proteins. Including the 13 sequences identified, the mouse Tas2r family contains approximately 30% more genes and 60% fewer pseudogenes than the human TAS2R family. Sequence and phylogenetic analyses of the proteins encoded by all mouse and human Tas2r genes indicate that TAS2R proteins present a lower degree of sequence conservation in mouse than in human and suggest a classification in five groups that may reflect a specialization in their functional activity to detect bitter compounds. Tas2r genes are organized in clusters in both mouse and human genomes, and an analysis of these clusters and phylogenetic analyses indicates that the five TAS2R protein groups were present prior to the divergence of the primate and rodent lineages. However, differences in subsequent evolutionary processes, including local duplications, interchromosomal duplications, divergence, and deletions, gave rise to species-specific sequences and shaped the diversity of the current TAS2R receptor families during mouse and human evolution.

Amino Acid Sequence↗
PubMed1998

Gustducin and its role in taste.

The mechanisms responsible for taste signal transductions are very complex. A key molecule, alpha-gustducin, a primarily taste-specific G protein alpha-subunit, was discovered in 1992 and was later found to be involved in both bitter and sweet taste transduction. A proposed mechanism for alpha-gustducin involves coupling specific cell-surface receptors with a cyclic nucleotide phosphodiesterase which would open a cyclic nucleotide-suppressible cation channel leading to influx of calcium, and ultimately leading to release of neurotransmitter. Although "knock-out" animals deficient in the alpha-gustducin gene clearly demonstrate that gustducin is an essential molecule for tasting certain bitter and sweet compounds, the precise role of alpha-gustducin in bitter and sweet taste is presently unclear. Indeed, there are several other signaling mechanisms in sweet and bitter taste, apparently unrelated to alpha-gustducin, that increase cyclic AMP or inositol 1,4,5 trisphosphate. Thus, proposed models for alpha-gustducin and those found by other laboratories may be parallel and interdependent.

Animals↗
PubMed2005

Haplotypes at the Tas2r locus on distal chromosome 6 vary with quinine taste sensitivity in inbred mice.

BACKGROUND: The detection of bitter-tasting compounds by the gustatory system is thought to alert animals to the presence of potentially toxic food. Some, if not all, bitter stimuli activate specific taste receptors, the T2Rs, which are expressed in subsets of taste receptor cells on the tongue and palate. However, there is evidence for both receptor-dependent and -independent transduction mechanisms for a number of bitter stimuli, including quinine hydrochloride (QHCl) and denatonium benzoate (DB). RESULTS: We used brief-access behavioral taste testing of BXD/Ty recombinant inbred (RI) mouse strains to map the major quantitative trait locus (QTL) for taste sensitivity to QHCl. This QTL is restricted to a ~5 Mb interval on chromosome 6 that includes 24 genes encoding T2Rs (Tas2rs). Tas2rs at this locus display in total 307 coding region single nucleotide polymorphisms (SNPs) between the two BXD/Ty RI parental strains, C57BL/6J (quinine-sensitive) and DBA/2J (quinine insensitive); approximately 50% of these mutations are silent. Individual RI lines contain exclusively either C57BL/6J or DBA/2J Tas2r alleles at this locus, and RI lines containing C57BL/6J Tas2r alleles are more sensitive to QHCl than are lines containing DBA/2J alleles. Thus, the entire Tas2r cluster comprises a large haplotype that correlates with quinine taster status. CONCLUSION: These studies, the first using a taste-salient assay to map the major QTL for quinine taste, indicate that a T2R-dependent transduction cascade is responsible for the majority of strain variance in quinine taste sensitivity. Furthermore, the large number of polymorphisms within coding exons of the Tas2r cluster, coupled with evidence that inbred strains exhibit largely similar bitter taste phenotypes, suggest that T2R receptors are quite tolerant to variation.

Animals↗