ch 15 part 1 Flashcards
do allosteric enzymes follow michaelis menten kinetics? yes/no and why/why not
allosteric enzymes do not follow the michaelis menten kinetics (exponential shape), because while other enzymes have a single polypeptide chain, allosteric enzymes have multiple polypeptide chains making their kinetics graph shape be a S shape.
what is a allosteric effector
a molecule that binds to the site of an allosteric enzyme, causing a change in configuration in enzyme activity.
what is a positive effector
increases enzyme activity
what is a negative effector
decreases enzyme activity
effectors can be what two things
homotropic or heterotropic
what is a homotropic effector
binds to the active site of the enzyme
what is a heterotropic effector
binds at a site other than the active site
what is one thing you need for enzyme cooperativity
you need to have multiple polypeptide chains
what is enzyme cooperativity
when the shape of one subunit of an enzyme consisting of several subunits is altered by the substrate
what can the binding of the substrate cause to enzyme cooperativity
the change can make you better at your job (positive cooperativity) or bad at your job (negative cooperativity).
positive cooperativity
when the shape of one subunit of an enzyme gets changed and this causes other subunits of the enzyme to change as well, making the job of the enzyme more efficient
negative cooperativity
when the shape of one subunit of an enzyme gets changed and this causes other subunits of the enzyme to change as well, making the job of the enzyme less efficient
what is feedback regulation
A process by which the product of a metabolic pathway influences its own production by controlling the amount and/or activity of one or more enzymes involved in the pathway.
what is positive feedback and why does it happen
a process by which the product of a metabolic pathway influences its own production by allowing the pathway to continue by binding to one enzyme that is part of the pathway. this can occur when there is not enough of the product from its pathway so it uses its own product to produce more
what is negative feedback
a process by which the product of a metabolic pathway influences its own production by blocking the process (by binding to an enzyme part of the pathway inhibiting the enzyme from doing its job) to diminish the amount of product in the body. this occurs when their is too much product in the body so it gives the body enough time to absorb it so once there isn’t enough, the product of the pathway restarts the process of making more.
what is phosphorylation/dephosphorylation?
a reversible mechanism to activate/deactivate an enzyme that attaches a phosphate group or removes it FROM ANY ANIMO ACID THAT CONTAINS AN OH GROUP LIKE SER, THR, and TYR
phosphorylation is what kind of reaction
condensation reaction that is reversible
dephosphorylation is what kind of reaction
hydrolysis that is reversible
what amino acids can go through phosphorylation/dephosphorylation?
SER, THR, TYR
what is a protein kinase
enzyme that attaches phosphorous group to SER, THR, and TYR
what is a phosphatase
enzyme that removes a phosphorous group from SER, THR, TYR
how are protein kinases and phosphatases different from zymogens
they are reversible mechanisms of action (reversible covalent bond) while zymogens are irreversible which creates an irreversible covalent bond
what are zymogens
inactive precursors of an enzyme, when turned into the active enzyme, this reaction is irreversible.
why could our body create zymogens
often times, our hormones are made in different locations from where theyre used like our digestive enzymes. our digestive enzymes are made in our pancreas and we know that our digestive enzyme’s are very acidic and strong and could burn our pancreas if created into the active form there. this way, our precursors are able to travel to our stomach without damaging other organs
what are some examples of zymogens in our bodies
proinsulin to insulin, prodigestive enzymes to active digestive enzymes, prothrombin to thrombim
go through the amplification cascade of our pancreatic proteases
- enteropeptidase creates trypsinogen 2. trypsinogen (inactive) creates trypsin (active) 3. trypsin (active) creates four different zymogens chymotrypsinogen, proelastase, procarboxypeptidase, and prolipase 4. these four zymogens creates chymotrypsin from chymotrypsinogen, elastase from proelastase, carboxypeptidase from procarboxypeptidase, and lipase from prolipase
what is the zymogen that gives to thrombin
prothrombin
what is the zymogen that gives to fibrin
fibrinogen
what is the zymogen that gives to lipase
prolipase
what is the zymogen that gives to carboxypeptidase
procarboxypeptidase
what is the zymogen that gives to chymotrypsin
chymotrypsinogen
what is the zymogen that gives to elastase
proelastase
what is the enzyme that comes from trypsinogen
trypsin
what is the enzyme that comes from proelastase
elastase
what is the enzyme that comes from chymotrypsinogen
chymotrypsin
what is the enzyme that comes from procarboxypeptidase
carboxypeptidase
what is the enzyme that comes from fibrinogen
fibrin
what is the enzyme that comes from prothrombin
thrombin
is this big substitution? His to ala
yes because you go from positive charge to neutral
A—(enzyme #1)–>B—(enzyme #2)–>C—(enzyme #3)–>D—(enzyme #4)
What does it mean if product D blocks its own synthesis
its an inhibitor which means this is negative feedback loop
A—(enzyme #1)–>B—(enzyme #2)–>C—(enzyme #3)–>D—(enzyme #4) What does it mean if product D accelerates its own synthesis
its an activator which means this is a positive feedback loop
what does big Km (K0.5) mean
low affinity, means alot of substrate present, lower enzymatic efficiency
what does low Km (K0.5) mean
high affinity, means limited substrate, higher enzymatic efficiency
in the ATCase pathway what enzyme is an activator and which one is an inhibitor
CTP is an inhibitor and ATP is an activator
What is Aspartate Carbamoyl Transferase, what process is it part of, and what step does this occur
an enzyme that adds a carbamoyl group to aspartate. this is the first step of pyrimidine biosynthesis
CTP is created in what pathway
pyrimindine pathways
ATP is created in what pathway
purine pathway
why does CTP do what it does
it acts as a feedback inhibitor on ATCase to allow the purine pathway to catch up on the pyrimidine pathway
why does ATP do what it does
it acts as a feedback activator on ATCase to start the pyrimidine pathway.
CTP and ATP is what kind of effector
CTP is a negative heterotropic effector and ATP is a positive heterotropic effector as they both compete for the allosteric site of the enzyme.
what is important to note about CTP and ATP
CTP is made in the pyrimidine pathway while ATP is made in the purine pathway
what is the concerted MWC model
- states that the allosteric enzyme can bind to the substrates (S) and sometimes to an activator (A) or an inhibitor (I).
- when anything binds to the enzyme, it causes changes that affect the equilibrium between the T and R forms.
3.as the equilibrium shifts, all subunits change conformation simultaneously and adopt the same conformation ALL IN ONE STEP.
what is t state
tense state of an enzyme that is inactive
what is r state
relaxed state of an enzyme that is active to bind
how does the T or R state occur.
The T state occurs when the inhibitor binds to the enzyme and the R state occurs when the activator binds to the enzyme.
what is the substrate in terms of the concerted model and effector status
it is a positive HOMOtropic effector that binds only to the R state at the active site
what is the activator in terms of the concerted model and effector status
it is a positive HETEROtropic effector that binds only to the R state at the allosteric site
what is the inhibitor in terms of the concerted model and effector status
it is a negative HETEROtropic effector that binds only to the T state at the allosteric site.
the activator stabilizes what form
the R form or the active form
the substate stabilizes what form
the R form or the active form
what is important to note about the allosteric regulation models
every time you bind anything to the enzyme (activator, inhibitor, or substrate), you create a different complex. so when you make a new complex, more of the regular enzyme (nothing bound)needs to be made to keep equilibrium.
what is the effector that stabilizes T state of ATCase
CTP is the inhibitor therefore the negative heterotropic effector
what is the effector that stabilizes R state of ATCase
ATPis the activator therefore the positive heterotropic effector
what is the substrate in ATCase
aspartate is the positive HOMOtropic effector
what is ATCase
an enzyme that moves a carbomyol group to asp.
what are the similarities between the concerted and sequential models of allosteric regulation
1) both state that R+T states exist of the enzyme
2) R state binds to the substrate more readily
what are the differences between the concerted and sequential models of allosteric regulation
Concerted model:
1) all subunits of enzyme change conformation simultaneously . you have all R or all T
Sequential model:
1) a change occurs in one subunit which triggers a change in the next subunit. you have some enzymes that are part R and part T.
greater affinity for the substrate means
positive cooperativity
lower affinity for the substrate means
negative cooperativity
what are isozymes
isomers of an enzyme that catalyze the same reaction in different environements.
