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Enzyme KineticsAnd
Inhibition
Biochemistry 2nd ed, Voet/Voet
Substrate Specificity
Substrate and Activesite are complementary
chemically.
hydrophobic
Biochemistry 2nd ed, Voet/Voet
Stereospecificity
Only one enantiomerwill fit correctly into
active site
Allosteric and Feedback Regulation of ACTase
ATP activates Enzyme
CTP inactivates Enzyme
Biochemistry 2nd ed, Voet/Voet
Lineweaver-Burke Plot
Competitive Inhibition
From Biochemistry, Matthews/VanHolde
Because the inhibitorcompetes with substrate,
Km is changed.
Vmax stays the samebecause ES EP
is same rateonce S is bound.
Competitive Inhibition
Non-Competitive Inhibition
From Biochemistry, Matthews/VanHolde
Because the inhibitorchanges the rate of
catalysis by inducing a conformational change in E, Vmax is changed.
Km stays the same because S binding is not
affected by I binding.
Non-competitive Inhibition
Mixed Inhibition
Inhibitor binds remotely from the active site but
changes both catalysis rate (Vmax) and substrate binding (Km)
CH
CH
O
CH
CH
CH2O
OHO
O-
O
P
C
C
C
N
NH
CN
CH
N
NH2
O
C
C
C
N
NH
CC
N
N
O CH3
CH2 CH2 CH3
OCH2CH3
SN
N
CH3
O
O
Phosphodiesterase Inhibitor
Smooth muscle cells relax:
NO. nitrous oxide ~ neurotransmitter
cGMP ~ cyclic GMP (top structure)
Intracellular Ca2+ concentration decreases
Muscle relaxation
If can get smooth muscle of blood vesselwalls to relax, then treat angina and high blood pressure
cGMP
Phosphodiesterases (PDE) cleave cGMP to GMPcausing muscle contraction
Inhibit PDE 5 (isozyme prevalent in vascular tissue)At least 9 isozymes.
Competitive inhibitor of PDE developed and marketedDidnt work well