Biochemistry- Enzyme Regulation and Inhibition Flashcards
What happens to the Km and Vmax Values with competitive inhibition? Where does the inhibitor bind?
Raise Km, Vmax= unchanged
binds to free enzyme (E)
Km and Vmax changes upon uncompetitive inhibitor binding. Where does is bind?
Decreases Km and Vmax. Binds to the ES complex
Km and Vmax changes after noncompetitive binding. Where does it bind?
Decreases Vmax, Km= Unchanged.
Binds to the free enzyme (E) or ES complex
Km and Vmax changes after mixed inhibitor binds. Where does it bind?
Increases or decreases Km, decreases Vmax. Binds to either E or ES complex, have a greater affinity for one vs the other, produce conformational changes in enzymes
Michaelis -Menten Equation
V0= Vmax [S]/ (Km + [S])
What does Km represent ?
michaelis constant, the concentration of the substrate when V0= Vmax/2: substrate concentration at which enzyme-catalyzed reaactions occur at 1/2 their mac velocity
What is the shape of a michaelis-menten kinetics plot?
hyperbolic
what does a low Km suggest?
the lower the Km, the higher the binding affinity of the enzyme to the substrate.
what is Kcat and how do you determine it?
Kcat= turnover number, represents # of substrate molecules converted to product by the enzyme.
formula : Kcat= Vmax/[E]total
what does a large Kcat signify?
larger the kcat, the more quickly the enzyme can catalyze the reaction= higher efficiency
kcat/ km ratio
the higher the ratio, the higher the efficiency
what is Ic50 and how do you determine it?
IC50= half maximal inhibitory concentration Ki = IC50 / (1 + ([S]/Km)) Ki= substrate concentration
what do points on the lineweaver burke plot represent?
- 1/ Km= x-intercept
1/ Vmax= Y- intercept
Lineweaver burke plot shape for competitive inhibitor
3 lines intercept at x intercept and -y intercept ( 1/ Vmax and -1/Km)
Lineweaver burke plot shape for uncompetitive inhibitor
All 3 lines are in parallel, do not touch
Lineweaver Burke plot shape for non-competitive inhibitors
3 lines intercept 1 x at - y intercept, run parallel through x -axis
what is positive cooperativity? Which type of curve does its plot have?
binding of one substrate shifts the enzyme from less active form to more active form , making it easier for second substrate to bind. Plot = sigmoidal curve
what is an enzyme cofactor?
covalently linked to the enzyme, are also called prosthetic groups or ligands
What does an oxidoreductase do?
catalyzes redox reactions
what does a transferase do?
transfers groups of atoms
what does a hydrolase do?
hydrolysis
what does a lyase do?
bond cleavage by means other than hydrolysis or oxidation to form a new double bond or ring structure
isomerase function
isomerization of molecules, converts between 2 isomers of a molecule
ligases or synthetases function
join 2 molecules
what are saturation kinetics?
when concentration of substrate is large enough for the substrate to occupy all the available active sites on the enzyme, plot plataeus
equilibrium constant formula for calculation
K= [C]^c* [D]^d / [A]^a*[B]^b
Equilibrium constant , K, meaning for reaction formation
K>1 , forward reaction favored , products
K<1 , reverse reaction favored, reactants
K=1, neither forward nor reverse are favored
what is catabolism? is it oxidation or reduction?
breakdown of molecules into smaller ones= oxidation
what does a lowering of a reaction’s Tm ( melting temperature), after adding an enzyme, suggest about the enzyme’s affect on molecular stability?
provides conformaitonal stability
what conditions are necessary to find the Kcat of a reaction? ( the substrate concentration should be….)
Saturating, Kcat is used to describe the rate-limiting step of catalysis under saturating conditions of substrate
phosphatase function
removes phosphate group
kinase function, also phosphorylase
attaches phosphate groups
