Term 1- Lec 12- Enzyme Regulation Flashcards
The rate limiting step of glycolysis is
Glucose to Glucose-6-P—this is an irreversible step
Product Inhibition at low [S]
Resembles comopetitive inhibition
Protuct Inhibition at high [S]
Competitive inhibition because the P far out number the S, thus inhibiting the enzyme.
T/F: Product Inhibition is a form of feedback inhibition?
It is not the same as feedback inhibition
The rate limiting step of gluconeogenesis is
Pyruvate to Phosphoenolpyruvate
How do allosteric and non-competitive inhibition differ?
NC Inhibition binds directly onto the enzyme. Allosteric inhibition binds a regulatory subunit connected to the enzyme or catalytic subunit
Km for allosteric enzymes is called
K0.5
What type of curves do allozteric enzymes exhibit and why
They exhibit sigmoidal curves and it is due to cooperative binding
Can Vmax for allosteric enzymes be altered?
Yes, Vmax can be altered depending on if an effector is bound and if it is activating or inhibiting
Can the affinity of an allosteric enzyme for a substrate (K0.5) be altered?
Yes, K0.5 can be altered depending on if an effector is bound and if it is activating or inhibiting
Result of activators on allosteric enzymes regarding K0.5 and Vmax
- K0.5 decreases (increased affinity)
* Vmax increases (more S can be reacted with)
Result of inhibitors on allosteric enzymes regarding K0.5 and Vmax
- K0.5 increases (decreased affinity)
* Vmax decreases (less S can be reacted with)
What type of effect does isoleucine (endproduct) have on threonine deaminase?
Isoleucine is feedback inhibiting threonine deaminase
What are the effectors of Aspartate Transcarbamoylase (ATCase)?
ATP and CTP
Which ATCase effector is the inhibitor, which state is ATCase in, and what type of relationship are they demonstrating?
- CTP
- T-state
- Feedback inhibition
Which ATCase effector is the activator, which state is ATCase in when bound to it, and what type of relationship are they demonstrating?
- ATP
- R-state
- Feed forward
Allosteric concerted model
The effector binds inducing conformational changes in the rest of the subunits of the protein
Allosteric sequential model
The effector binds one subunit making the neighboring subunits more susceptible to change (similar to Hemeglobin)
Allosteric regulation model: Modulation
The effector binds, inducing a conformational change that creates a binding site that wasn’t there before.
Allosteric regulation model: Fusion
Effector binds causing conformational change in separate protein all together.
Calmodulin has what effect on what enzyme?
Calmodulin activates Glycogen Phosphorylase (GP)
Why does elastin breakdown in smoker’s cells
Methionine is oxidized on ∂1-antiproteinase, blocking it’s ability to bind and inactivate elastase. Free elastase over time destroys the lung tissue causing emphysema.
Chemical donor and target(s) for Phosphorylation
ATP. Serine, Threonine, Tyrosine, and Histidine
Chemical donor and target(s) for Adenylation
ATP. Tyrosine
Chemical donor and target(s) for Uridylylation
UTP. Tyrosine
Chemical donor and target(s) for ADP-Ribosylation
NAD. Arginine, Glutamine, Cysteine, and modified Histidine
Chemical donor and target(s) for Methylation
S-Adenosyl methionine (SAM). Glutamic acid
Explain Glycogen phosphorylase (GP) regulation
GP is phosphorylated by GP Kinase to become more active. GP is dephosphorylated by GP phosphatatse to become less active
Limited Proteolysis acts via covalent or non-covalent interactions?
Covalent interactions
One-time, irreversible and highly selective cleaving of a polypeptide chain by a protease
Limited Proteolysis
What is the name of the precursor form of a digestiv enzyme?
Proenzyme or zymogen
Limited Proteolysis acts on what type of molecules?
Proenzymes or zymogens to cleave them into their active form
Explain how Chymotripsinogen becomes Chymotripsin
The protease trypsin cleaves chym.ogen into two fragments. The large fragment cleaves intself into two fragments and those 3 fragments covalently link to form active chymotrypsin
Constitutive enzymes
Enzymes whose concentrations remain essentially constant over time
Covalent interactions with enzymes: Modifications
Addition of feature to specific residues ie. Adenylation = add’n of P from ATP onto tyrosine
The 2 ways to change enzyme abundance
Protein synthesis and protein degredation
