Allostery and Regulation I Flashcards
What is allosterism?
Controlling when binding of small molecules helps to control the activity of enzyme.
The substrate is affecting the enzyme by its binding.
What are allosteric switches related to? ON or OFF OR volume switches?
volume switches
What is covalent modification
When you make or break covalent bonds. When you break a peptide bond you usually activate something
What happens if there isn’t a substrate available for the enzyme?
If the substrate is not available then there is no way the enzyme can be active.
If the km is high the you will need ___ of substrate to activate the enzyme.
a lot
What types of plots do allosteric enzymes give?
Give sigmoidal plots
What types of plots do Homotropic Effectors give?
These give sigmodial curves, so the substrate affects the enzyme.
What types of plots do Heterotropic Effectors give?
Models noncompetitive plots.
What are homotrophic effectors?
They are substrates and effectors that affect an enzyme.
What is an example of a homotrophic effector of ATCase? and what does it favor?
Aspartate
Binding of Aspartate by ATCase Favors the R-state so additional Substrate Binding is Favored.
What are heterotrophic effectors?
Heterotrophic effectors are not the substrate of an enzyme, but do affect the enzyme.
What is an example of a heterotrophic effector?
Activator (ATP)
Inhibitor (CTP)
What type of subunits do ATCase contain? and what do they bind to?
Contains 6 regulatory subunits
ATP and CTP bind to regulatory sites
Contains 6 catalytic subunits
Aspartate bind to catalytic subunits and favors R state
What does ATCase catalyze?
and what step does play in synthesizing pyrimidine nucleotides
CTP, UTP, DDTP
It starts with Carbomoyl Phoshate and its end product is an intermediate (Carbamoyl Aspartate ) that is necessary to synthesize pyrimidine nucleotides. IT’S THE FIRST STEP IN MAKING PYRIMIDINE NUCLEOTIDES.
How does ATP affect ATCase?
In the Presence of ATP, the V0 is increased compared to No ATP
ATP activates ATCase (converts to R State)
How does CTP affect ATCase?
This indicates that you have plenty pyrimidines and that you need to start making purines.
CTP Reduces the activity of ATCase- Converts to T State
V0 decreases as [CTP] increases
Aspartate is a Substrate of ATCase. So how does the concentration of aspartate affect the activity of ATCase.
At Low [S], ATCase in T State
At High [S], ATCase mostly in R State
As [S] increases, ATCase increasingly in R State
When is ATCase most active?
ATCase is most active when energy (ATP) is high, When Pyrimidines (make CTP) are Low in concentration relative to purines (make ATP)
What determines if CTP inhibits ATCase or ATP activating it? Who wins the race?
Km and Concentration
This is evidence of complementary
What are zymogens?
Inactive forms of enzymes
How are zymogens activated?
They are activated by cutting specific peptide bonds that allow for access of the substrate to the active site. Its an ON/OFF switch. There is a cascade system where at each level you have a chain of enzymes that get activated.
What is an example of zymogen being activated?
o Chymotrypsinogen (inactive) ♣ Trypsin- Peptide bond Broken at 15-16
o Pie-Chymotrypsin (Partly Active)
♣ Acts on Pie-Chymotrypsin and cuts at 146-149
o Alpha-Chymotrypsin (Fully Active)
♣ We lose 147-148
♣ The active site is becoming fully exposed.
