Sweet and savory Flashcards
what are the 4 types of sugar replacement categories we saw in class ?
-low-calorie sweeteners (obesity) -non-glucose-based sweeteners (diabetes) -more natural sweeteners (i.e. stevia) -high-potency sweeteners
T or F : the sweet and umami are taste with T2R
flase, both taste are tasted with dimers of T1R2, T1R1 or T1R3
T or F : mGluRs also recognize the umami compound L-Glu
true and so the mGluR1 is used in 3D modeling of the receptor to study the response of certain ligands
T or F: 3D structure of mGluR1 has been used to model the structure of other T1Rs (i.e. T1R1)
true
how is the L-glutamate bound by the T1R ?
it is bound due to its 2 carboxylic groups
Sweet perception is due to the dimerisation of __ and ___
T1R2 / T1R3
umami perception is due to the dimerisation of __ and ___
T1R1 / T1R3
T or F : the sweet and bitter taste can’t be tasted by the same cells
true, the expression of T1R and T2R do not overlapp in cells
What is the role of IMP in the taste perception of umami?
it is a taste enhancer of umami ; it reduces the EC50 of umami perception. IT is a allosteric modulator and on its own it doesn’t produce a response
What are the two regions of the T1R
The TMD : terminal trans-membrane domain with 7 trans-membrane helices
The VTD : venus flytrap domain with its upper and lower lobes
T or F : the sweet/umami receptor is one protein with two domains (1 gene) while bitter receptor is only a protein with one domain (1 gene)
true
on which domain is located the hinge region of the T1R
in the VFTD
L-glutamate binds in the ___ region of the VFTD
hinge
The conformation of the VFTD is ___ when the ligand is bound
closed
How does the IMP has an enahncement acitivity ?
it binds the VFTD and stabilize the closed form (active form)
What is bonito bushi made from ?
either from dired kombu and bonito or from mushroom and dried kombu
** exams : what are the steps involved in making the bonito bushi ?
-1 Boiling : musculature cut from body and gently boiled for 1 hour
-2 Smoking : hot smoking above hardwood (oak) fire for 10-20 days
-3 Fermentation : after inoculation with Aspergillus, Eurotium, Penicilliumsurface fermentation for ~2 weeks
-4 Sun drying : sun-drying for 2 days, after which mold is scraped off
The molding process repeated 3-4 times and after a total of 3-5 months, meat is light brown and dense, and sounds like a resonant piece of wood
Lactoyl GMP has an extra ___ group on the NH2
lactic acid
Acetyl GMP has an extra ___ group on the NH2
acetyl group
___ also enhances salty while ___ only enhances umami
salty+umami : lactoyl GMP
umami only : Acetyl GMP
This molecule is the main contributor to the scallop taste :
R-strombine
R-strombine is formed naturally from a.a ____ and ____
glycine and pyruvic acid
what are the synthetic and bio-synthetic route of making R-strombine?
What is the differences between R-strombine and S-strombine
R-strombine : The methyl of the chiral carbon is pointing backwards
S-strombine : methyl group of the chiral carbon is pointing forward, methalic taste
using synthetic route, what are the two buildiing blocks of R-strombine ?
glycoxylic acid and R-alanine
Why does the flavour industry doesn’t want the s-strombine in their food ?
becaus the s-strombine has a metalic taste
alapyridaine is a Maillard reaction product formed upon heating of ___ and ____
alanine and hexose
what is a multi-modal taste enhancer ?
will change the taste perception (often enhancement) multiple other tastes. For example pyridaine with the sweet, umami and salty taste enhancing effect
in the case of alapyridaine, the ___ form is not active
r-form not active while the s form is active. So the stereochemistry matters for the tast enhancement effect.
What is the reason that pyridaine is not used in the industry
the reason that pyridaine was not used by companies is that it needs to be added in the same amount than the molecule it is enhancing (for example if sucrose than it would mean that you add a lot and so it is too expensive)
The relative sweetness RS is a way to compare sweet molecules to ____
sucrose
What are the steps involved in the processing of bitter neohesperidin from citrus peel into the sweet version
1- C-ring opening by strong alakali environment
2- stabilization of the chalcone by hydrogenation
____ seem to underlie inter-individual variation in taste perception
the haplotypes
Most AA sequence variation T1Rs in first _____, implicated in ligand recognition
extracellular domain
T2Rs carry AA variation in_____ , where they bind the bitter tastants
trans-membrane domains
what could explain the large inter-individual variance observed in tasting sweetness
there is a lot of variant of the T1R2 (haplotype)
True of False : an haplotype automatically leads to an inter-individual variation in taste perception
false, it doens’t necessaly lead to a different specificity pf te receptor. Haplotype only means that there is a a.a changed in the seqeuence of the receptor
why was it thought that the histidine of neoculin were involved in the taste modifying property of neoculin ?
because the sweetness response curve of neoculin ressemble the protonation curve of histidine
how does the pH of neoculin influences the conformation of the protein ?
the protein is active in the open conformation. At Acidic pH, the majority of the a.a in the subunits (histidine, arginine and lysine) are positive and so there is repulsion between the two sub-unit keeping the protein in its active configuration
T or F : removing the histidine for an alanine keeps the protein in its active configuration and the neoculin will be active at neutral pH
true
____ can only bind small sweeteners while ____ has larger cavity and can bind a larger collection of non-proteic sweeteners
T1R2 : small sweetners
T1R3: larger cavity and can bind non-proteic bigger and proteic molecules
What is the name of the broad sweet blocker seen in class
lactisole
T or F : lactisole has an effect on all sweetners known
true
how does the lactisole blocks the sweet taste perception
binds with the histidine of the c-terminal of the Rc and forms a salt bridge. Also, the CH3 of the lactisole binds with the alanine fo the receptir and keep it in the locked position (open/inactive)
where does each of the ligand binds on the T1R2/T1R3 receptor
____ binds : e.g. sucrose, aspartame, neotame
___ binds : e.g. sucrose
___ binds : cyclamate, NHDC
___ binds : sweet proteins
Site I (T1R2): e.g. sucrose, aspartame, neotame
Site II (T1R3): e.g. sucrose
Site III (TMD of T1R3): cyclamate, NHDC
Site IV (T1R3): sweet proteins
T or F : you could have synergy of two large sweetners
false, synergy is only observed between two small sweetners or a small and a large sweetner
how does lactisole blocks (physically) the receptor
Lactisole(sweet blocker) might lock T1R3 in resting state, preventing conformational changes of heterodimer leading to signal transduction
what is the effect of lactisole on the cyclamate response and on the aspartame response
cyclamate (binding to the TMD of T1R3 like lactisole)
aspartame (binding to the site I of the T1R2)
lactisole inhibits cyclamate by :
lactisole inhibits aspartame by :
inbitition of cyclamate by : competitive
inhibition of aspartame by : allosteric modulation / negative cooperativity
in cometitive inhibition what happens to the following :
- EC50 :
- signal amplitude
- EC50 shift to the left
- No reduction of the signal amplitude
in allosteric inhibition what happens to the following :
- EC50 :
- signal amplitude
No shift in the EC50
reductiion in the amplitude of the signal
Can NHDC and cyclamate boost the response to sucrose ?
yes, by allosteric modulation since they both bind the site III of the T1R3 and sucrose also binds the site I (like aspartame and lactisole).
Synergy between sucrose and NHDC or cyclamate is an example of ___ modulation of sweet response
positive allosteric
why can’t the synergy be used in the case of zero-calorie sweetners ?
synergy is often only observed at lower sweetner levels
__ is a PAM that binds the VFTD of T1R2, away from the hinge region
SE-2 (indified by high throughput screening)
what is the effect of SE-2 on the sucralose response ?
lowers the sucralose sweetness even when sucralose is present in sub-optimal concentrations
t or f : SE-2 produces a sweet response on its own by binding the VFTD of the T1R2
false, it does not produce a sweet response on its own although it is right that is binds the T1R2 region close to the hinge in the receptor
