Umami taste transduction mechanisms  

Oleh:

Kinnamon, Sue C.

Jenis: Article from Journal - ilmiah internasional
Dalam koleksi: The American Journal of Clinical Nutrition vol. 90 no. 03(S) (Sep. 2009), page 753S-755S.
Topik: Umami; transduction

Ketersediaan

Perpustakaan FK Nomor Panggil: A07.K.2009.03 Non-tandon: 1 (dapat dipinjam: 0) Tandon: tidak ada

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Isi artikel

L-Glutamate elicits the umami taste sensation, now recognized as a fifth distinct taste quality. A characteristic feature of umami taste is its potentiation by 5'-ribonucleotides such as guanosine-5'-monophosphate and inosine 5'-monophosphate, which also elicit the umami taste on their own. Recent data suggest that multiple G protein–coupled receptors contribute to umami taste. This review will focus on events downstream of the umami taste receptors. Ligand binding leads to Gß{gamma} activation of phospholipase C ß2, which produces the second messengers inositol trisphosphate and diacylglycerol. Inositol trisphosphate binds to the type III inositol trisphosphate receptor, which causes the release of Ca2+ from intracellular stores and Ca2+-dependent activation of a monovalent-selective cation channel, TRPM5. TRPM5 is believed to depolarize taste cells, which leads to the release of ATP, which activates ionotropic purinergic receptors on gustatory afferent nerve fibers. This model is supported by knockout of the relevant signaling effectors as well as physiologic studies of isolated taste cells. Concomitant with the molecular studies, physiologic studies show that L-glutamate elicits increases in intracellular Ca2+ in isolated taste cells and that the source of the Ca2+ is release from intracellular stores. Both G{alpha} gustducin and G{alpha} transducin are involved in umami signaling, because the knockout of either subunit compromises responses to umami stimuli. Both {alpha}-gustducin and {alpha}-transducin activate phosphodiesterases to decrease intracellular cAMP. The target of cAMP in umami transduction is not known, but membrane-permeant analogs of cAMP antagonize electrophysiologic responses to umami stimuli in isolated taste cells, which suggests that cAMP may have a modulatory role in umami signaling.

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