Enzyme Regulation Flashcards
Enzyme ___ is the ability of an enzyme to catalyze only one particular reaction
specificity
Specificity is due to the ____ ____ of enzyme and substrate
structural complementarity
The substrate glucose is bound to the active site of what enzyme?
hexokinase
What hypothesis considers that the enzyme’s active site is modified/flexible upon binding of the substrate?
induced fit
What hypothesis considers that the enzyme as the lock and the substrate fits in as the key?
lock and key
What are the four mechanisms of enzyme regulation?
genetic control, covalent modification, specialized controls , allosteric regulation
___ controls the amount of enzyme (gene induction of repression)
Genetic
____ ____ is the attachment of chemical groups such as phosphate groups
Covalent modification
Zymogens, isozymes, and modular proteins are examples of what?
Specialized controls
__ ___ is an inhibitor or activator binds to the enzyme at a site different than the active site.
Allosteric regulation
The phosphate groups are attached through the ___ side chains of amino acids, such as serine.
-OH
What donates the phosphate molecule in the attachment of a phosphate group via covalent modification?
ATP
The reversible covalent attachment of phosphate groups ____ enzyme actitivy
regulates
Protein ___ is an enzyme that adds a phosphate group to an enzyme
kinase
Protein __ is an enzyme that removes a phosphate group from an enzyme
phosphatase
Enzyme is catalytically inactive when the phosphate is ___
attached
Enzyme is catalytically active when the phosphate is ___
removed
The phosphate group addition affects protein __
folding
The __ ___ ___ is removed from the enzyme when adding a phosphate group
amino acid sidechain
Phosphate ___ the active site of an enzyme, making it inactive
closes
Attachment of phosphate groups can be ___
reversed
Zymogens are _____
proenzymes
___ are inactive precursors of enzymes or other proteins that acquire full activity by specific cleavage of one or more peptide bonds of the protein
Zymogens
Zymogens are ___ precursors of enzymes
inactive
Zymogens have ___ ____ of one or more peptide bonds of the protein
specific cleavage
Three examples of zymogens:
- Insulin
- Proteolytic enzymes
- Blood clotting factors
Insulin, proteolytic enzymes, and blood clotting factors are examples of ____
zymogens
Insulin is generated by ___ of a specific peptide from ____
removal, proinsulin
The activation of insulin is by the ___ of a specific peptide from the ___ ___ molecule.
removal, inactive proinsulin
Proteolytic enzymes of the ___ ___ are synthesized as zymogens in the pancreas and stomach
digestive tract
Blood clotting factors are produced by activation of zymogens of ___ ____ ___
blood clotting factors
____ are synthesized as zymogens in the pancreas and stomach
proteolytic
Activation of insulin by the ____ of a specific peptide from the ____ proinsulin molecule
removal, inactive
___ is a peptide hormone
insulin
Insulin is the active form of ___
proinsulin
Trypsin originates in the ___
pancreas
Chymotrypsin originates in the ___
pancreas
Carboxypeptidase originates in the __
pancreas
Elastase originates in the ___
pancreas
Pepsin originates in the ___
stomach !!
What is the active protein of trypsinogen?
trypsin
What is the active protein of chymotrypsinogen?
chymotrypsin
What is the active protein of procarboxypeptidase?
carboxypeptidase
What is the active protein of proelastase?
elastase
What is the active protein of pepsinogen?
pepsin
What is the zymogen of the active protein trypsin?
trypsinogen
What is the zymogen of the active protein chymotrypsin?
chymotrypsinogen
What is the zymogen of the active protein carboxypeptidase?
procarboxypeptidase
What is the zymogen of the active protein elastase?
proelastase
What is the zymogen of the active protein pepsin?
pepsinogen
In the proteolytic activation of chymotrypsinogen, peptide bonds are ___ at the ends
cut
Chymotrypsin attacks __ in the proteolytic activation process
itself
___ chymotrypsin is the fully active form
alpha
Chymotrypsin’s proteins are connected by what type of bonds?
disulfide bonds
The zymogen activation steps lead to __ ___ ____
blood clot formation
What are the two blood clot formation pathways?
extrinsic/tissue factor
intrinsic/contract activation
Fibrinogen is __ in blood
soluble
Fibrin is ___ in blood
insoluble
Fibrin forms __ __
blood clots
An active factor activates an ___ ___
inactive factor
___ activates blood clotting factors in the intrinsic pathway
proteases
___ are forms of an enzyme that differ in their quaternary structure, with different numbers of distinct polypeptide subunits.
Isozymes
Isozymes are forms of an ___ that differ in their ____ ___, with different numbers of distinct ____ ____.
enzyme, quaternary structure, polypeptide subunits
Lactase dehydrogenase is an example of what?
isozyme
There are __ different subunits of LDH
5
__ __ LDH is mainly A4 isozyme
skeletal muscle
A4 isozyme is ____
skeletal muscle
___ __ LDH is mainly B4 isozyme
heart muscle
B4 isozyme is ___
heart muscle
Skeletal muscle LDH produces___ __ in ___ conditions
lactic acid in anaerobic
Heart muscles LSD uses __ __ in ___ conditions
lactic acid in aerobic
The two isozymes of LDH work in __ directions
opposite
__ ___ are proteins that bind to enzymes and influence their activity
modulator proteins
Modulator proteins __ ___ and ___ the active site of enzymes
cover up and inhibit
cAMP-dependent protein kinase are examples of what?
modulator proteins
cAMP-dependent protein kinase are made up of __ and ___
catalytic subunits (C)
regulatory subunits (R)
In cAMP-dependent protein kinase, catalytic subunits are ___ active
enzymatically
In cAMP-dependent protein kinase, regulatory subunits are ___ ___ that bind the to __ subunits and ___ their activity
modulatory proteins, C, inhibit
The modulator protein prevents the ___ from binding to the __ __ and being converted into a product module
substrate, active site
in cAMP dependent protein kinase, the R subunits __ C subunit activity
inhibit
cAMP dependent protein kinase is active when R subunits are ___
disconnected
___ ___is the inhibition or activation of enzyme activity through non covalent binding of small molecules to a site different than the active site of the enzyme
allosteric regulation
allosteric regulation is the ___ or ___ of enzyme activity
inhibition or activation
allosteric regulation occurs through __ ___ ___ of small molecules to a site __ than the active site of the enzyme
non covalent binding, different
__ __ is when the final product F binds to enzyme 1 and inhibits enzyme 1(allosteric enzyme)
feedback inhibition
___ ___ shuts down the pathway and prevents further synthesis of final product F.
feedback inhibition
Final product F is non competitive inhibitor making it an ___ ___
allosteric enzyme
Feedback inhibition is what type of regulation?
Non competitive
What is the graph shape of allosteric enzymes?
sigmoid/S shaped curve s
What is the s shaped curve of allosteric enzymes caused by?
cooperative binding
“allo” means a ____ site
different
cooperative binding occurs because allosteric enzymes are composed of __ __
multiple subunits
Regulatory molecules (allosteric enzymes), including feedback inhibitors, bind to the enzymes and __ or __ their activity
inhibit or stimulate
Allosteric effectors change the ___ structure of the subunit polypeptides and/or change the ____ interactions
3D, subunit
Allosteric effectors change the 3D structure of the __ ___ and/or change the ___ interactions
subunit polypeptides, subunit
A sigmoid (s shaped curve) is produced by ___ ___ of substrate molecules to an ___ ___
cooperative binding, allosteric enzyme
For an allosteric enzyme, the more substrates there is more __ states are converted into __ states
T (taut), R (relaxed)
For allosteric enzymes, the __ state is inactive
T (taut)
For allosteric enzymes, the __ states is active
R (relaxed)
The existence of _ and _ states of an allosteric enzyme can account for __ __ of substrate molecules and the S-shaped curves
T and R, cooperative binding
Dimer is …
Two subunits side by side
R state of an allosteric enzyme __ bind substrates
can
T state of an allosteric enzyme ___ bind substrates
cannot
T state an allosteric enzyme can convert to the __ state
R
When T state is converted to the R state, more ___ are open, producing more ___
substrates, products
