Lecture 14: Enzyme Regulation Flashcards
How are metabolic enzymes regulated?
compartmentalization: different locations
enzyme concentration: on/off switch
enzyme activity: volume control
hormone signals and second messengers: master regulators
Substrate level control acts on a _____ reaction
single
Feedback control targets a ________ in the pathway
different step
Activators ____ more products
promote
Inhibitors ____ more products
prevent
What do isozymes do?
catalyze the same reaction but with different efficiencies
What do reversible covalent modifications do?
add 1+ functional groups to activate/inactive the enzyme
What is the donor molecule in phosphorylation modification?
ATP
What is an example of a modified protein in phosphorylation modification?
glycogen phosphorylase
Protein function of phosphorylation modification
glucose homeostasis; energy transduction
Donor molecule of acetylation modification
acetyl CoA
Example of modified protein in acetylation modification
histones
protein function of acetylation modification
DNA packing; transcription
Donor molecule of myristoylation modification
myristoyl CoA
myristoylation modification example of modified protein
Src
myristoylation modification protein function
signal transduction
ADP ribosylation donor molecule
NAD+
ADP ribosylation example of modified protein
RNA polymerase
ADP ribosylation protein function
transcription
Farnesylation modification donor molecule
farnesyl pyrophosphate
Farnesylation modification example of modified protein
Ras
Farnesylation modification protein function
signal transduction
gamma- Carboxylation modification donor molecule
HCO3-
gamma- Carboxylation modification example of modified protein
thrombin
gamma- Carboxylation modification protein function
blood clotting
Sulfation modification donor molecule
3’-phophoadenosine-5’-phophosulfate
Sulfation modification example of modified protein
fibrinogen
Sulfation modification protein function
blood clot formation
ubiquitination modification donor molecule
ubiquitin
ubiquitination modification example of modified protein
cyclin
ubiquitination modification protein function
control of cell cycle
Why is phosphorylation activating?
- thermodynamics: ATP hydrolysis can drive unfavorable reactions
- kinetics: physiological processes dictate reaction rate
- cell processes: ATP amounts dictated by metabolism (energy charge), signal transduction amplification (catalytic turnover)
- shape and charge complementarity: each phosphate adds (-2) charge and (3+) H-bonds
Kinases _____ phosphates
ADD
phosphatase ____ phosphates
REMOVE
Allosteric binding does or does not occur at the active site?
does not
Heteroallostery definition
effector binds at the allosteric site
Homoallostery definiton
cooperatively
Binding of CTP to ACTase prefers what site?
T/inactive site
Binding of ATP prefers to ACTase prefers what site?
R/active site
histone acetylation ______ transcription
promotes
histone phosphorylation _____ transcription
prevents
Histone methylation does what for transcription?
promotes or prevents
