E3 Module 7 Flashcards
Can enzyme regulation be stimulatory inhibitory or both?
What are the results of this?
Enzyme regulation could be stimulatory, resulting in an overall increase in enzyme activity, or it could be inhibitory, resulting in a decrease in enzyme activity.
Enzyme regulation is mediated by:
- bioavailability of enzymes in different tissues and cellular compartments
-control of catalytic efficiency through binding of regulatory molecules
-covalent modification
-proteolytic processing
What type of control of enzyme activity often involves the binding of small molecules (metabolites) to regulatory sites on the enzyme located outside of the active site?
allosteric
Name the processes affecting enzyme bioavailability
RNA synthesis, processing, protein synthesis, protein degradation, and protein targeting.
What is catalytic efficiency regulated by
inhibition, allosteric control, covalent modification, and proteolytic processing
Enzymes are subject to ____________ _____________ due to noncovalent binding of small molecules, and _______________ ______________, in which the inhibitory molecule forms a covalent bond in the enzyme active site
reversible inhibition
irreversible inhibition
What are the three classes of reversible inhibitors?
Competitive inhibitors, uncompetitive inhibitors, and mixed inhibitors.
With increasing concentration of a competitive inhibitor, the apparent ______ of the enzyme increases, reflecting the requirement of higher substrate concentration to reach ________, however, not the _______
competitive inhibitior
Km
1/2 Vmax
not Vmax
Competitive inhibition is characterized by
inhibitors that bind to the free enzyme and inhibit substrate binding at the active site
Uncompetitive inhibitors decrease both the ______ and apparent ____ kinetic parameters by the same factor; uncompetitive inhibition is/is not overcome by increasing substrate concentration
Vmax and Km decrease
is not overcome by increasing substrate concentration
Mixed inhibitors are similar to ____________ inhibiotrs in that they bind to sites distinct from the active site. The difference is that mixed inhibitors can bind to both ____________ and ______________. _________________ is a rare case of mixed inhibition.
uncompetitive
enzyme and the enzyme substrate complex
Noncompetitive inhibition
What prevents hydrated Na+ and K+ ions from passing through the nicotinic acetylcholine receptor channel in the absence of acetylcholine?
A ring of nonpolar amino acids in the interior chamber prevents the hydrated ions from moving through the constricted channel.
name the functional component of the receptor type: nicotinic acetylcholine receptor
opening of the inner chamber to facilitate ion transport
name the functional component of the receptor type: receptor tyrosine kinase
autophosphorylation of the cytoplasmic tail and binding of adaptor proteins to Tyr-P
name the functional component of the receptor type: nuclear receptor
transcriptional regulation of downstream target genes
name the functional component of the receptor type: G-protein coupled receptor
GDP-GTP exchange and dissociation of the heterotrimeric G protein
name the functional component of the receptor type: Tumor necrosis factor receptor
assembly of adaptor complexes through TNF receptor-associated death domain proteins
describe the 8 steps of signaling events showing how glucagon binding to glucagon receptors in liver cells increases blood glucose levels in between meals.
- Glucagon binds to the N-terminal
- The C-terminal domain undergoes a conformational change
- The GDP bound heterotrimeric G protein binds to the receptor
- GDP is exchanged for GTP in the G-alpha subunit
- The G alpha and G beta/gamma subunits dissociate
- the G alpha subunit binds to activate adenylate cyclase
- Production of cyclic AMP leads to activation of PKA
- PKA phosphorylates downstream proteins that control glucose transport.
Based on the Butowt, R. and von Bartheld, C.S. (2020) paper:
a) what might explain why ~60% of COVID-19 patients do not experience anosmia even though they experience other symptoms of SARS-CoV-2 infection?
b) what might explain why ~10% of COVID-19 patients with anosmia do not regain their sense of smell even after 3 months?
a) The olfactory support cells were not infected and/or killed by the virus.
b) The stem cells needed to replenish olfactory support cells were killed.
LO - Differentiate between the three classes of reversible inhibitors
LO - recognize the difference between the kinetics of reversible inhibitors using Lineweaver–Burk plots
LO - Identify the roles of ATP and CTP in the regulation of aspartate transcarbamoylase (ATCase)
ATP - shifts line in V0 vs substrate concentration graph to the left, stimulates ATCase activity
CTP - shifts line to the right, inhibits ATCase activity
What happens when ATP binds to the regulatory subunit of an enzyme in comparison to CTP?
When ATP binds to the subunit of the enzyme, it shifts ATCase to the activated R state, whereas CTP binding to the regulatory subunit stabilizes the inactive T state conformation.
LO - the role of allosteric regulation and covalent modification in ATCase activity
covalent modification
-phosphorylation
-adenylylation
-uridylylation
In the unphosporylated T state conformation, is glycogen phosphorylase active or inactive? What about the R state
inactive in T state, active in R state
What happens during the most common form of covalent modification of enzymes, phosphorylation of Ser, Thr, Tyr residues by kinase enzymes
it adds a negative charge to the enzyme through the addition of inorganic phosphate (PO3^2-)
Regulation of enzyme activity by proteolytic cleavage is by its very nature an…
irreversible process
LO - Define the components of a cell signaling pathway
receptor protein - activated and leads to the modification of intracellular target proteins
target proteins - intracellular, control a variety of cellular responses
first messengers
upstream and downstream signaling proteins
second messengers
LO - the difference between first and second messengers
first messengers - not all peptide hormones, some are lipids and steroids, and others are even smaller like nitric oxide, Ca2+, and CO2-
second messengers - signal amplification, involves enzymes that catalytically activate downstream signaling proteins, many of which are also enzymes cyclic AMP
LO - Compare G-protein coupled receptors, receptor tyrosine kinases, and ligand-gated ion channels
LO - Distinguish between the shared pathways and parallel pathways of glucagon and epinephrine activity
LO - Explain the differences between the GDP-bound and GTP-bound states of the G subunit
LO - identify key steps in protein kinase A activation
LO - guanine nucleotide exchange factor
LO - GTPase activating protein
LO - G protein receptor kinase
LO - adrenergic receptor kinase
LO - arrestin
low Kd = _______ affinity
high Kd = _______ affinity
high
low
describe best case scenario for inhibitor development
low Kd, competitive inhibitor
A phosphodiesterase inhibitor will prevent degradation of ________ to __________.
cAMP to AMP
Adenylate cyclase is the enzyme that converts _____ to _______.
ATP to cAMP
How does addition of CTP effect ATCase activity?
inhibits ATCase activity
moves graph to the right
How does addition of ATP affect ATCase activity
stimulates ATCase activity
moves graph to the left
cGMP is a ________ messenger for vasodilation. Increased NO leads to ________ cGMP, which activates protein kinase G. Sildenafil, or Viagra, prolongs vasodilation by _________ cGMP phosphodiesterase. cGMP phosphodiesterase _______ cGMP and ________ vasodilation. By inhibiting this enzyme, the concentration cGMP remains _________ and vasodilation is prolonged.
cGMP is a secondary messenger for vasodilation. Increased NO leads to increased cGMP, which activates protein kinase G. Sildenafil, or Viagra, prolongs vasodilation by inhibiting cGMP phosphodiesterase. cGMP phosphodiesterase degrades cGMP and decreases vasodilation. By inhibiting this enzyme, the concentration cGMP remains higher and vasodilation is prolonged.
