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LF130
L26: Allosteric Regulation and Commercialisation of enzymes
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Pandan Panda
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Cards (50)
What is the full name of the enzyme referred to as ATCase?
Aspartate transcarbamoylase
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Why is catalysis by ATCase considered the rate-limiting step in pyrimidine biosynthesis?
Because it alters its catalytic activity in response to cellular levels of
CTP
and
ATP
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What effect does CTP have on ATCase activity?
CTP
decreases
activity
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What effect does ATP have on ATCase activity?
ATP
increases
activity
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What happens to the curve when 0.4 mM CTP is added?
The curve shifts to the
right
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What happens to the curve when 2 mM ATP is added?
The curve shifts to the
left
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What type of kinetics does ATCase exhibit?
Non-
Michaelis-Menten
kinetics
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What does increasing concentrations of CTP do to the apparent Km for aspartate?
It
increases
the apparent Km for
aspartate
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How can allosteric interaction of ATCase be examined?
Through structural studies using an inhibitor called
PALA
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What does PALA mimic in the study of ATCase?
PALA mimics the reaction
intermediate
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What state does PALA stimulate the formation of in ATCase?
The R,
relaxed
state
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What is the activity level of the T state of ATCase?
Low
activity
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What is the activity level of the R state of ATCase?
High activity
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What does allosteric regulation of ATCase involve?
Equilibrium
between the
R and T states
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What effect does CTP binding have on ATCase?
It stimulates an
allosteric
shift to the
T state
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What effect does ATP binding have on ATCase?
It stimulates an
allosteric
shift to the
R state
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What is the key enzyme in glycolysis mentioned in the material?
Pyruvate kinase
(PK)
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What metabolic process occurs when glucose is in short supply?
Gluconeogenesis
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What is the relationship between glycolysis and gluconeogenesis?
They are interconnected
metabolic
pathways
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What is a futile cycle in metabolism?
A cycle where
glycolysis
and
gluconeogenesis
occur simultaneously without net gain
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What is feed forward activation in the context of pyruvate kinase?
PK is activated by an early intermediate in glycolysis,
FBP
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What is feedback inhibition in the context of pyruvate kinase?
PK is inhibited by an end product,
ATP
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What is the summary of allosteric regulation?
Allosteric regulation makes
enzymes
'switchable'
Binding of
effectors
to
secondary sites
alters activity
Effectors can be activators or inhibitors
Changes operate through conformational changes affecting the active site
Displays non-
Michaelis-Menten kinetics
with
co-operativity
Regulates flux of
metabolites
through pathways
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What are some applications of enzymes mentioned in the material?
Enzymes are used in farming, food industry,
biosensors
, and therapeutics
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Why are shikimate pathways attractive targets for antimicrobial agents and herbicides?
They are absent in
animals
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What is the mechanism of action of glyphosate as a herbicide?
Glyphosate inhibits
EPSP synthase
in a
competitive
manner
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What is the purpose of genetic engineering in crops to be Roundup resistant?
To fuse the bacterial gene encoding
CP4 EPSP synthase
to a
chloroplast signal peptide
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What was the first Roundup Ready commercial crop?
Roundup Ready
soybeans
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What are some pros and cons of glyphosate-resistant crops?
Pros include reduced tilling and increased
profits
; cons include lower
yield
and potential increased herbicide resistance in weeds
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What is the first approved GMO herbicide-resistant crop?
Roundup Ready
soybeans
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What are some sources of enzymes for food applications mentioned in the material?
Traditional sources include intact
microbes
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What are some applications of enzymes in the food industry?
Cheese making
High
fructose
corn syrup production
Aspartame production
Other food processing applications
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What was the yield difference of Roundup Ready soybean crops compared to conventional varieties in 1999?
Roundup Ready soybean crops had a
6.7%
lower yield.
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What are some approved GMO herbicide resistant crops and their uses?
Alfalfa: Animal feed (
USA
, approved 2005)
Canola: Cooking oil, margarine (USA, approved
1995
)
Cotton: Fibre, cottonseed oil (USA, approved 1994)
Maize: Animal feed, high-fructose corn syrup (USA, approved 1995)
Soybean: Animal feed, soybean oil (USA, approved
1993
)
Sugar Beet: Food (USA, approved
1998
)
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Who delivered Lecture 26 on enzymes in the context of the food industry?
Robert Spooner
.
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What are the sources of enzymes for food applications?
Traditional: Using intact microbes (e.g.,
lactobacilli
,
S. cerevisiae
, Aspergillus oryzae)
Increasingly: Enzymes or enzyme mixtures added to bioreactors
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What is the structure of cow's milk and its main components?
Water
:
85.5
-
89.5
%
Fat:
2.5
-
6%
Protein:
2.9
- 5% (
80%
casein
)
Lactose:
3.6
- 5.5%
Minerals:
0.6
-
0.9
%
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What role does chymosin play in milk structure?
Chymosin cleaves
κ-casein
, destabilizing
micelles
and allowing milk to clot.
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What is the enzyme classification number for chymosin?
EC
3.4.23.4
.
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What are the benefits of using recombinant chymosin in cheese production?
High production yield
Better curd texture
Reduced bitterness
Suitable for
kosher
and
halal
certification
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