Enzyme Kinetics Flashcards
2 Mechs of Enzymes Decreasing DeltaG (and kind of effect each is)
Ground state destabilization (DeltaH effect)
Transition state stabilization (DeltaS effect)
4 Mechs of Catalysis (and 1 major point)
General Acid/Base Catalysis Electrostatic catalysis Covalent catalysis Entropy - All chemical rxns entail charge redistribution
2 Properties of Enzyme Active Sites
Invaginated pocket to position things close, DeltaS effect
Microenvironment affects ionization status (pKa) of enzyme and substrate groups
2 Reasons Why Initial Velocity Must be Taken Immediately
- [A] is well approximated by [A]i
2. Amount of [P] is negligible and won’t interfere
Requirement for Continuous Assays (2)
Ability to measure either disappearance of substrate or appearance of product
“Coupled” Continuous Assays (2)
For when substrate-products have no spectroscopic properties - couple a given product to a rxn that does yield spectroscopic properties
Discontinuous Assay (reason & method)
When substrate-product exhibits similar/no spectroscopic properties
Radiolabel substrate, quench the rxn at different times, wash away radiolabeled substrate and measure product
kcat
Turnover number, maximum number of substrate molecules converted to product per unit time
Km
Michaelis constant, substrate concentration [A] that yields 1/2 Vmax
kcat/Km
Specificity constant
2 Conclusions of Competitive Inhibitors
kcat independent of [I[
Km increases linear w/ [I]
2 Conclusions of Uncompetitive Inhibition
kcat decreases hyperbolic w/ [I]
Km decreases hyperbolic w/ [I]
2 Conclusions of Noncompetitive Inhibition
kcat decreases hyperbolic w/ [I]
Km independent of [I]
Conclusion of Enzyme w/ Multiple Active Sites w/ No Cooperativity
Impossible to kinetically distinguish b/w 1 mole of enzyme w/ n identical sites and n moles of enzyme with a single site
Main Conclusion of Enzymes w/ Multiple Active Sites w/ Positive Cooperativity
Provides enhanced sensitivity to changes in [A] in narrow physiological range (S-shaped curve)
