Enzyme kinetics Flashcards
Enzyme properties vs system properties?
Enzyme properties: attributed to one single enzyme reaction within a cellular system.
System properties: properties that result from all reactions within a cellular system . E.g. growth rate, which is the activity of all integrated enzymatic reactions
What is the formula for the gibbs free energy?
deltaG = deltaG0 (standaardcondities) + RTln([p]/[s])
What determines the outcome?
Whether the reaction is forward or backwards or in eq.
deltaG<0 = forward. S->P deltaG>0 = backwards. P->S deltaG=0 = eq.
What is the simplest scheme for enzyme analysis? (That you start with with Michaelis menten)
S + E ES -> E + P
What is the 1st assuption of the michaelis menten equation?
1) The rate of product formation is irreversible. (k-2 = 0)
What is the 2nd assumption?
ES formation = ES breakdown. v1 = v2. d[ES]/t = -d[ES]/t.
What is the 3rd assumption?
total enzyme concentration [e] = [E] + [ES]
What is the 4th assumption?
[S»»»»>e
What does the Km mean?
Km = [S] at which half of the Vmax is reached. Km = measure of affinity for the enzyme. The higher the Km value, the lower the affinity.
What does the lineweaver burk equation do? What can you determine with it?
Relates 1/v to 1/s. Linear relationship. 1/v = 1/vmax + ks/vmax * 1/[S]
What is the cross point at the x-axis and the cross point at the y-axis? What is the slope? (lineweaver burk)
x-axis: 1/Vmax
Y-axis: -1/Km
Slope = Km/Vmax
What do competitive inhibitors do in terms of Michaelis menten?
Increase Km (lower affinity). Inhibitor competers for the reaction center. Same Vmax, different Km. At high [S], the inhibitor is outcompeted.
What does a noncompetitive inhibitor change in terms of lineweaver burk?
Same Km, but decreased Vmax. Reaction center is still open (same affinity), but the effective enzyme activity is reduced.
Uncompetitive inhibitor?
Decrease Km and Vmax. Inhibitor binds to ES complex, substrate gets locked in: effective enzyme concentration reduced.
