Lecture 2: Enzyme Catalysis Flashcards
Substrate Recognition by Enzymes
-complementary Interactions between substrate and enzyme
-involves induced fit
-Binding (site is a small region)
-similar factors apply to inhibitors and drugs
Substate x enzyme Interactions
-highly complementary
-hydrophobic to hydrophobic
-H bonding
-Coulombic interactions
Induced fit
-conformational change in enzyme for substrate binding (free vs bound)
-optimal recognition of substrates
-brings in important residues
Enzyme inhibition
disruption of catalytic function
Catalytic Function
E+S <-k1+2-> E-S –k3-> E+P
+I +I
E-I <———> E-S-I
v0
-initial velocity
-measured with constant [E]
Lineweaver Burk Plot
1/v0 =1/Vmax + Km/Vmax
-inverse
-straight line
Enzyme Inhibitior Types
competitive, mixed (noncompetitive), uncompetitive
Competitive inhibition
-interferes with active site
-binds only free E
-V max same
-KM different
-graph slope flatter than regular rate
Mixed Inhibition
-competitive and uncompetitive inhibitors
-binds E and E-S complex
-completes catalytic function
-same effect as using less enzyme
-Vmax changes if EI and ESI equilibrium smae
Uncompetitive inhbition
-changes shape of enzyme
-Vmax and KM decrease
-binds only E-S complex
Which choice best describes
competitive binding between the enzyme
substrate, S, and inhibitor, I?
All of the above
-I binds active site
-I binding site partially overlaps with active site
-I induces change that prevents S bonding
Apparent Vmax and Km
-change by (1+[I]/KI)
KI
=[E][I]/[E x I]
Apparent catalytic constants due to COMPETITIVE inhibition
Km= Km(1+ [I]/K1)
