Enzymes Flashcards
Synthase
No ATP needed
Phosphatase
uses H2O to remove phosphoryl group
Synthetase
Requires ATP
Phosphorylase
uses Pi to break bond and make phosphorylated product
Oxidase
uses O2 as acceptor without adding it to a reaction
Oxygenase
1 or 2 O atoms added
Dehydrogenase
Electron acceptor in redox reaction (NAD+ and FAD+)
Coenzymes
organic molecules required by some enzymes
Cofactors
Inorganic substances required for or to increase rate of catalysis
Holoenzyme
enzyme + nonprotein
active
Apoenzyme
enzyme without nonprotein
inactive
Km
amount of substrate needed to reach 1/2 Vmax
Small Km
high affinity for substrate
low conc needed to reach 1/2 Vmax
High Km
low affinity for substrate
more conc of substrate needed to reach 1/2 Vmax
Relationship of [E] to Vo and Vmax
directly related
2E = 2Vo and 2Vmax
1st Order
[S] much lower than Km
velocity proportional to [S]
0 Order
[S] much greater than Km
velocity is constant and equal to Vmax and is independent of [S]
Km and Vmax on Lineweaver-Burk
Increase= closer to 0 decrease= further away from 0
Irreversible Inhibitor
binds E covalently
can only recover E by making a new E
Reversible Inhibitor
binds E noncovalently
easy recovery of E
Suicide Inhibitor E
converts inhibitor into a reactive form in active site
Competitive Inhibition effect on Vmax and Km
no effect on Vmax
Km increases
HMG CoA-reductase
rate limiting enzyme in cholesterol biosynthesis
Statin Drugs
structural analogs of HMG- CoA reductase
compete for active site
lower plasma cholesterol levels
