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83 Cards in this Set
- Front
- Back
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what do enzymes serve as
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diagnostic tools
therapeutic targets |
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what are the properties of enzymes
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biological catalyst
regulated highly specific |
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what are the parameters of an enzyme reaction
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rate of reaction
equilibrium |
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what do enzymes effect
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only rate of reaction
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what does equilibrium tell you
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the direction of the reaction, it doesn't tell you anything about rate of reaction
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do enzymes effect standard free energy
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no
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what is the capacity of a system to do work at a constant temp/pressure
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gibbs free energy
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how do enzymes bring the transition state lower
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by decreasing free energy of activation of the transition state
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what does the rate of rxn depend on
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free energy of activation of the transition state
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what is the free energy of activation equal to
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free energy of transition state - free energy level of substrate
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what are the factors that effect enzymatic activity
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pH and temperature
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how does pH effect enzymatic activity
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change in pH can lead to protonation/deprotonation of amino acids etc which results in a change of charge which may cause a conformational change and change the enzymes activity
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what is the body's optimum pH
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6.8-7.4
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what is the pH of pepsin
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1.5-2
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what is not effected by change in pH
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papain
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how does temperature effect enzymatic activity
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by messing with the H bonds which are required to stabilize the 3-D structure of the enzyme
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what is activity
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micro moles / min
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what is specific activity
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micro moles/min / mg protein
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what happens as the specific activity increases
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the purity/concentration of the enzyme increases
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what aids enzymes in functioning
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co factors
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organic co factors
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co enzymes
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prosthetic group
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coenzymes or metal ions that are covalently bound to the enzyme
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what are holoenzymes
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catalytically active enzymes together w/ a coenzyme or metal ion
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what are enzymes highly specific for
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type of reaction
substrate it binds to and reaction it catalyzes |
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what is the region of the enzyme that binds the substrate and contains the AA that participate in breaking bonds
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active site
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what does Vmax tell us
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the concentration of enzyme
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what is the y intercept on the Double reciprocal plot?
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1/vmax
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what is the x intercept on the Double reciprocal plot?
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1/km
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what is the slope on the Double reciprocal plot?
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km/vmax
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what happens at vmax
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steady state in which activity won't go higher
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what does km tells us
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the affinity of the drug to the enzyme (higher the affinity the lower the km)
and the substrate concentration at which reaction rate is half of the vmax |
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how can enzymes be inhibited
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reversibly or irreversibly
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what is an example of irreversible inhibition and how does it work
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nerve gas/insecticide
works by using DIPF to bind to serine of AChE and there by inhibiting its activity |
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what kind of bonding occurs in irreversible inhibition
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covalent and noncovalent bonding
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how does irreversible inhibition work
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it works by tightly binding either covalently or noncovalenty to the AA of the active site or important AA on other parts of the enzyme and dissociating from the enzyme very slowly
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how does reversible inhibition work
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the inhibitor binds to the enzyme via weak interactions and dissociates rapidly
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what is it called reversible inhibition
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because you can change some of the conditions to overcome the inhibition
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what type of bonding is there in irreversible inhibition
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noncovalent and covalent
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what type of bonding is there in reversible inhibition
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noncovalent only
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what are the types of reversible inhibition
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competitive, uncompetitive, noncompetitive.
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what is competitive inhibition
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it is competition between two molecules (the natural substrate and a molecule analogous to the structure of the natural substrate) for the active site of the enzyme
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how can competitive inhibition be reversed
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it can be reversed by increasing the concentrations of one of the two molecules
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what happens to vmax and km in competitive inhibition
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Vmax stays the same
Km increases therefore affinity decreases |
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what happens to the x and y intercept in competitive inhibition
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x intercept increases but y intercept stays the same
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what happens to the activity of the enzyme in competitive inhibition
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the activity of the enzyme decreases but can be overcome by increasing substrate concentration
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which kind of inhibition does the inhibitor HAVE to bind to the active site
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competitive inhibition
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where does the inhibitor bind to in uncompetitive inhibition
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only to the ES complex
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what happens to the rate of the reaction in and the enzyme activity in uncompetitive inhibition
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rate of reaction and enzyme activity increase
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what happens in uncompetitive inhibition
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the inhibitor binds to the ES complex and stabilizes it making the enzyme activity go faster
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what happens to km and vmax in uncompetitive inhibition
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they both change
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where does the inhibitor bind to in uncompetitive inhibition
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ONLY to the ES complex
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what happens in noncompetitive inhibition
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inhibitor binds to ES or enzyme and doesn't have to bind to active site, but it can if it needs to
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what happens to km and vmax in noncompetitive inhibition
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vmax changes
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how are enzymes regulated
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feedback inhibition
regulatory proteins covalent modification proteolytic activation gene expression/regulation |
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what occurs in feedback inhibition
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occurs in allosteric enzymes and happens when the body makes too much of a molecule and results in that molecule binding to the regulatory site stoping the enzyme from functioning
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what occurs in regulatory proteins
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proteins either inhibit or stimulate enzyme activity
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what is an example of regulatory proteins
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Ca activating Calmodulin which in turns activates MLCK
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what occurs in covalent modification
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covalent attachment of phophoryl group either inhibits or stimulates a enzyme
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what is the most dominant regulatory mechanism
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covalent modification
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what carries out phosphorilation
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kinase
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what carries out dephosphorilation
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phosphatases
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what are the AA tha can be phosphorylated
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Ser, Tyr, Thr
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what happens in proteolytic activation (digestion)
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some enzymes are made and stored as inactive precursers and when they are needed they are digested(hydrolyzed) into their active forms (active form is smaller than inactive form)
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what are the names of the precursers
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zymogen or proenzyme
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what hydrolyzes the inactive enzymes in proteolytic activation
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other enzymes
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what are the properties of allosteric regulation of proteins
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don't follow michaelis-menton equation
have sigmoidal curve cooperative interaction more than one binding site |
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what causes the sigmoidal cure in allosteric enzymes
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cooperative interaction of the subunits of the enzyme
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what is O2 in myoglobin and O2 in hemoglobin
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myoglobin = normal enzyme hyperbola
hemoglobin = allosteric enzyme sigmoidal |
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what are the two models that describe allosteric interaction between enzyme units
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sequential and concerted
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what are the two types of allosteric regulation and what are the differences
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heterotropic is regulation by a molecule that isn't the substrate (negative or positive)
homotropic is regulation by the substrate (always positive) |
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what is the all or none type of allosteric regulation
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concerted
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what is positive regulation in heterotropic allosteric regulation
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T > R
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what is negative regulation in heterotropic allosteric regulation
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R > T
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where does the substrate or nonsubstrate bind to in heterotropic and homotropic regulation
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active site
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what are the properties of the T form
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lower affinity for substrate
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what are the properties of the R form
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high affinity for the substrate
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what is the sequential model
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the substrate binds to one subunit causing a transition from T > R but doesnt cause this to happen in other subunits but it does result in the affinity of the substrate to the next subunit to increase
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what is the concerted model
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binding of a substrate to the first subunit leads to a change in all the subunits from T > R and increase in affinity for the substrate
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what do the allosteric activators and inhibitors do
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activator T > R
inhibitor R > T |
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what does a shift to the right mean and what causes it
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decrease in rate
cause by CTP |
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what does a shift to the left mean and what causes it
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increase in rate
caused by ATP |
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is ATP a positive or negative heterotropic effect
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positive
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is CTP a positive or negative heterotropic effect
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negative
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