Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
FIGURE 5.8
The biochemical transduction path of the sweet stimulus. GTP — guanosine triphosphate
coupled to G-regulatory protein; α, β, and γ — G protein subunits; ATP — adenosine
triphosphate; cAMP — cyclic adenosine monophosphate; AC — adenylyl cyclase; PLC —
phospholipase C; PIP 2 — phosphatidylinositol biphosphate; IP 3 — inositol triphosphate.
N
N
N
O O O O
N
O N
O
O
P O
O
OH
FIGURE 5.9 Transformation of adenosine triphosphate into cyclic adenosine monophosphate
(cAMP) under the influence of adenylyl cyclase.
OH
NH2 NH2
OH OH OH
N
adenylyl cyclase
O O
H
P P P CH CH
2 O N 2 N P P
O O O
OH + HO
OH OH
OH OH
ATP
cATP
such a case, the artificial sweetener is adsorbed in a nonsugar receptor box. The
arising stimulus is transferred to G-type protein, which activates phospholipase C
(PLC). The latter, acting on phosphatidylinositol biphosphate (PIP 2), produces IP3
as a second messenger, which phosphorylates the intracellular plasma and produces
an increase in the activity of Ca 2+ ions in the receptor cell. 16 Intracellular Ca 2+ ions
activate sweet-taste nerve fibers, leading to neurotransmitter release.
REFERENCES
AC
K +
Sugar
Sug
Recp
β
ATP
γ
α
PIP2 PLC
GTP
IP3 γ
β
cAMP
α
Ca 2+
PKA
Ca 2+
NSug
Recp
Sweet Taste
Sensory Nerve Fiber
Artificial
Sugar
1. Acree, T.E., Chemical senses, Part 2, in Handbook of Sensory Physiology, Vol. 4,
Beidler, L.M., Ed., Springer-Verlag, Berlin, 1971.
2. Shallenberger, R.S. and Acree, T.E., Molecular theory of sweet taste, Nature, 216,
480, 1967.
Ca 2+