Enzymology
enzymes increase reactions by lowering the activation energy-which is the energy needed to
go from the reactant to the transition state. The transition state is called the enzyme
substrate complex - correct answer-function of enzymes
Classes of enzymes: oxidoreductase-oxidation/reduction reactions, transferase-group
transfer reaction, hydrolase-hydrolytic reactions, lyase- cleavage of C-C C-S C-N bonds,
isomerase- isomerization, ligase-condensation of two molecules coupled with cleavage of
ATP. - correct answer-class of enzymes
complex=haloenzyme=protein+cofactor. If the co-factor is an organic compound it is called a
co-enzyme. If the co-enzyme is tightly bound cofactor=prosthetic group. Other wise a
co-substrate. Co-factors beside coenzymes are essential ions. If loosely bound they are
called activator ions, if tightly bound they are called metalloenzymes - correct
answer-complex enzyme
precursos to enzyme that needs to be cleaved to be activated. - correct answer-zymogen
when more than one enzyme works together to catalyze one reaction. - correct
answer-multienzyme complex
when one enzyme catalyzes multiple steps of a reaction - correct answer-multifunctional
enzyme
actice site is what binds the substrate. Induced fit model, the binding of substrate induces
conformational change such that the enzyme fits around the substrate as much as the
substrate fits into the active site. There is also the lock and key model where it's a perfect
fit-not used as much anymore - correct answer-induced fit vs lock and key
pH away from optimal pH can slow down reaction. How to figure out what pH is the best, you
just test out a specific buffer at different pH's then record the time, the fastest time=optimal
pH. Extreme pH can lead to denaturation - correct answer-affect of pH
temperature: rise increase rate of reaction, but also the rate of destruction of the protein.
Q10= rate of reaction at (x+10)degrees Celsius/rate at x degrees celcius. In humans rate
usually doubles per 10 degrees. - correct answer-affect of temp
[E]: more enzyme, faster reaction. Linear relationship between the amount of enzyme and
velocity of reaction, constant + slope. An increase in [E] will lead to an increase in activity
everytime. - correct answer-affect of [E]
[S]: is a diminishing returns. Michaelis-menten: substrate starts to undergo reaction as you
add it into the system, the more you add the faster it goes and then plateaus( hyperbola
Vi=Vmax[S]/[km+[S]] where ½ Vmax= Km). Sigmoidal Kinetics: you need a threshhold
, amount of substrate to start the reaction. Once you reach that it increases velocity and then
plateaus. - correct answer-Affect of [S]
Enzyme Substrate interactions: E+S=ES -> EP=E+P where ES is the enzyme substrate
complex/transition state. The rate at which this transition state is reached can be affected by
multiple factors.
Proximity and orientation: reaction happens at random so proximity increases if you have
more reactants. You are more likely to react if there are more things to react with in the
solution. They also have to be oriented a certain way. - correct answer-interaction of E/S
once the enzyme binds to the substrate, it may undergo conformational change making it
resemble the transition state which would lower the activation energy - correct answer-bond
strain catalysis
an enzyme might covalently bond to a substrate and transfer that substrate to react with
another substrate to form the prodcut, acting as a transferring enzyme. - correct
answer-covalent catalysis
histidine and other AA that can undergo Acid Base reactions transfer protons which
catalyzes the reaction - correct answer-Acid/base catalysis
allosteric: enzymes may have other binding sites besides the active site and this site is used
for regulation. This can be done by substrate, an inhibitor or activators. If it is the substrate
that is doing the regulation, it is called a homotorphic effector. Usually +effectors. Example of
mechanism seen in hemoglobin and O2. Heterotrophic effectors are effectors other than the
substrate. - correct answer-allosteric regulation
Negative feedback regulation is when a product downstream allosterically binds to the
enzyme slowing down the reaction because enough of the product has been made. Negative
feedback inhibition is the complete stop of the reaction. - correct answer-negative feedback
regulation
done to increase/decrease activity. The most common example is phosphoralation which
changes protein conformation because the phosphate is - charged so interacts with +
charged residues resulting in the exposure of the active site. Removal of the phoshate group
by the phosphotase. Another way that an emzyme is modified by another enyzyme is the
activation of zymogens. They are made inactive, they need to be cleaved to be activated. An
example is trypsin from tripsinogen. Trypsin is further used to activate other zymogens. -
correct answer-covalent modifications
Enzyme unit is the concentration of the enzyme that can catalyze 1 uM of substrate into
product in one minute. Mesured in katal. - correct answer-enzyme unit
enzyme units/mg of protein. - correct answer-specific activity
maximum activity. How much substrate into product at Vmax. - correct answer-turnover
number
enzymes increase reactions by lowering the activation energy-which is the energy needed to
go from the reactant to the transition state. The transition state is called the enzyme
substrate complex - correct answer-function of enzymes
Classes of enzymes: oxidoreductase-oxidation/reduction reactions, transferase-group
transfer reaction, hydrolase-hydrolytic reactions, lyase- cleavage of C-C C-S C-N bonds,
isomerase- isomerization, ligase-condensation of two molecules coupled with cleavage of
ATP. - correct answer-class of enzymes
complex=haloenzyme=protein+cofactor. If the co-factor is an organic compound it is called a
co-enzyme. If the co-enzyme is tightly bound cofactor=prosthetic group. Other wise a
co-substrate. Co-factors beside coenzymes are essential ions. If loosely bound they are
called activator ions, if tightly bound they are called metalloenzymes - correct
answer-complex enzyme
precursos to enzyme that needs to be cleaved to be activated. - correct answer-zymogen
when more than one enzyme works together to catalyze one reaction. - correct
answer-multienzyme complex
when one enzyme catalyzes multiple steps of a reaction - correct answer-multifunctional
enzyme
actice site is what binds the substrate. Induced fit model, the binding of substrate induces
conformational change such that the enzyme fits around the substrate as much as the
substrate fits into the active site. There is also the lock and key model where it's a perfect
fit-not used as much anymore - correct answer-induced fit vs lock and key
pH away from optimal pH can slow down reaction. How to figure out what pH is the best, you
just test out a specific buffer at different pH's then record the time, the fastest time=optimal
pH. Extreme pH can lead to denaturation - correct answer-affect of pH
temperature: rise increase rate of reaction, but also the rate of destruction of the protein.
Q10= rate of reaction at (x+10)degrees Celsius/rate at x degrees celcius. In humans rate
usually doubles per 10 degrees. - correct answer-affect of temp
[E]: more enzyme, faster reaction. Linear relationship between the amount of enzyme and
velocity of reaction, constant + slope. An increase in [E] will lead to an increase in activity
everytime. - correct answer-affect of [E]
[S]: is a diminishing returns. Michaelis-menten: substrate starts to undergo reaction as you
add it into the system, the more you add the faster it goes and then plateaus( hyperbola
Vi=Vmax[S]/[km+[S]] where ½ Vmax= Km). Sigmoidal Kinetics: you need a threshhold
, amount of substrate to start the reaction. Once you reach that it increases velocity and then
plateaus. - correct answer-Affect of [S]
Enzyme Substrate interactions: E+S=ES -> EP=E+P where ES is the enzyme substrate
complex/transition state. The rate at which this transition state is reached can be affected by
multiple factors.
Proximity and orientation: reaction happens at random so proximity increases if you have
more reactants. You are more likely to react if there are more things to react with in the
solution. They also have to be oriented a certain way. - correct answer-interaction of E/S
once the enzyme binds to the substrate, it may undergo conformational change making it
resemble the transition state which would lower the activation energy - correct answer-bond
strain catalysis
an enzyme might covalently bond to a substrate and transfer that substrate to react with
another substrate to form the prodcut, acting as a transferring enzyme. - correct
answer-covalent catalysis
histidine and other AA that can undergo Acid Base reactions transfer protons which
catalyzes the reaction - correct answer-Acid/base catalysis
allosteric: enzymes may have other binding sites besides the active site and this site is used
for regulation. This can be done by substrate, an inhibitor or activators. If it is the substrate
that is doing the regulation, it is called a homotorphic effector. Usually +effectors. Example of
mechanism seen in hemoglobin and O2. Heterotrophic effectors are effectors other than the
substrate. - correct answer-allosteric regulation
Negative feedback regulation is when a product downstream allosterically binds to the
enzyme slowing down the reaction because enough of the product has been made. Negative
feedback inhibition is the complete stop of the reaction. - correct answer-negative feedback
regulation
done to increase/decrease activity. The most common example is phosphoralation which
changes protein conformation because the phosphate is - charged so interacts with +
charged residues resulting in the exposure of the active site. Removal of the phoshate group
by the phosphotase. Another way that an emzyme is modified by another enyzyme is the
activation of zymogens. They are made inactive, they need to be cleaved to be activated. An
example is trypsin from tripsinogen. Trypsin is further used to activate other zymogens. -
correct answer-covalent modifications
Enzyme unit is the concentration of the enzyme that can catalyze 1 uM of substrate into
product in one minute. Mesured in katal. - correct answer-enzyme unit
enzyme units/mg of protein. - correct answer-specific activity
maximum activity. How much substrate into product at Vmax. - correct answer-turnover
number
