Taste receptor binding

Theoretical sensory sweetness and bitterness scores for the two theories are described below for mixed solutions of sweet and sour. This exercise considers the case of a mixture of 20 mM D-phenylalanine (D-PA) and 60 mM L-phenylalanine (L-PA). Individually each of these solutions yield a sensory score of 5.0, i.e. the sweetness of 30 mM D-PA is 5 and the bitterness score of 60 mM L-PA is 5. Theoretically, if both compounds bind independendy at different taste receptors, the sweetness and bitterness should each be 5. On the oAer hand, if both compound bind at the same taste receptor in a competitive manner, die sweetness and bitterness scores should decrcase. In regards to the latter, the sweet and bitter compound were mixed in a ration of 1 3 (20 mM to 60 mM) which yields a probability of fitting a taste receptor of l-in-4 for sweet and 3-in-4 for bitter. If these probabilities are multiplied by the original concentrations, i.e. 20 mM and 60 mM, the products would be in the expected concentration of 5 mM (1/4 of 20mM) and 45 mM (3/4 of 60mM). The sweetness of a 5 mM solution and the bitterness of a 45 mM solution corresponds to a sensory score of 2 and 3, respectively, and represent the expected sensory score for the competitive hypothesis. 

Sweet-tasting molecule (S) binds to sweet-taste receptor (SR), activating the G protein gustducin (Ggust). 

QSAR and molecular modelling will contribute signficantly to the characterisation of ligand-binding sites of both intracellular and taste receptors for ecdysteroids. 

Morini G, Bassoli A, Temussi PA (2005) From small sweeteners to sweet proteins anatomy of the binding sites of the human T1R2 T1R3 receptor. J Med Chem 48 5520-5529 Nelson G, Hoon MA, Chandrashekar J, Zhang Y, Ryba NJ, Zuker CS (2001) Mammalian sweet taste receptors. Cell 106 381-390... 

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