Perceptual variation in umami taste and polymorphisms in TAS1R taste receptor genes.
BACKGROUND
The TAS1R1 and TAS1R3 G protein-coupled receptors are believed to function in combination as a heteromeric glutamate taste receptor in humans.


OBJECTIVE
We hypothesized that variations in the umami perception of glutamate would correlate with variations in the sequence of these 2 genes, if they contribute directly to umami taste.


METHODS
In this study, we first characterized the general sensitivity to glutamate in a sample population of 242 subjects. We performed these experiments by sequencing the coding regions of the genomic TAS1R1 and TAS1R3 genes in a separate set of 87 individuals who were tested repeatedly with monopotassium glutamate (MPG) solutions. Last, we tested the role of the candidate umami taste receptor hTAS1R1-hTAS1R3 in a functional expression assay.


RESULTS
A subset of subjects displays extremes of sensitivity, and a battery of different psychophysical tests validated this observation. Statistical analysis showed that the rare T allele of single nucleotide polymorphism (SNP) R757C in TAS1R3 led to a doubling of umami ratings of 25 mmol MPG/L. Other suggestive SNPs of TAS1R3 include the A allele of A5T and the A allele of R247H, which both resulted in an approximate doubling of umami ratings of 200 mmol MPG/L. We confirmed the potential role of the human TAS1R1-TAS1R3 heteromer receptor in umami taste by recording responses, specifically to l-glutamate and inosine 5'-monophosphate (IMP) mixtures in a heterologous expression assay in HEK (human embryonic kidney) T cells.


CONCLUSIONS
There is a reliable and valid variation in human umami taste of l-glutamate. Variations in perception of umami taste correlated with variations in the human TAS1R3 gene. The putative human taste receptor TAS1R1-TAS1R3 responds specifically to l-glutamate mixed with the ribonucleotide IMP. Thus, this receptor likely contributes to human umami taste perception.
Chen
Qing-Ying
QY
Monell Chemical Senses Center, Philadelphia, PA 19104, USA.
Alarcon
Suzanne
S
Tharp
Anilet
A
Ahmed
Osama M
OM
Estrella
Nelsa L
NL
Greene
Tiffani A
TA
Rucker
Joseph
J
Breslin
Paul A S
PA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D005260:Female; D014644:Genetic Variation; D018698:Glutamic Acid; D006801:Humans; D007291:Inosine Monophosphate; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D017470:Receptors, Glutamate / Q000235:genetics* / Q000502:physiology; D013601:T-Lymphocytes / Q000378:metabolism; D013649:Taste / Q000235:genetics* / Q000502:physiology; D055697:Taste Perception / Q000235:genetics* / Q000502:physiology; D013652:Taste Threshold / Q000235:genetics / Q000502:physiology; D055815:Young Adult
D043562:Receptors, G-Protein-Coupled; D017470:Receptors, Glutamate; C431926:taste receptors, type 1; D007291:Inosine Monophosphate; D018698:Glutamic Acid