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BG McGraw-Hill: Gilbert, Basic Concepts in Biochemistry, JN 5036
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C H A P T E R
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ENZYME KINETICS
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S, P, and E (Substrate, Product, Enzyme)
Amounts and Concentrations
Active Site
Assay
Velocity
Initial Velocity
Mechanism
Little k’s
Michaelis-Menten Equation
Vmax
kcat
Km
Special Points
kcat/Km
Rate Accelerations
Steady-State Approximation
Transformations and Graphs
Inhibition
Allosterism and Cooperativity
The Monod-Wyman-Changeaux Model
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Basic Concepts in Biochemistry
BG McGraw-Hill: Gilbert, Basic Concepts in Biochemistry, JN 5036
Kinetics seems scary, but understanding just a few things spells relief.
Two problems with kinetics are the screwy (and often unexplained) units
and the concepts of rate and rate constant. And you can’t ignore enzyme
kinetics; it forms the foundation of metabolic regulation, provides a diag-
nostic measure of tissue damage, and lies at the heart of drug design and
therapy.
The most well-studied enzyme catalyzes the reaction SsP. The
kinetic question is how time influences the amount of S and P. In the
absence of enzyme, the conversion of S to P is slow and uncontrolled. In
the presence of a specific enzyme (S-to-Pase1), S is converted swiftly and
specifically to product. S-to-Pase is specific; it will not convert A to B
or X to Y. Enzymes also provide a rate acceleration. If you compare the
rate of a chemical reaction in solution with the rate of the same reaction
with the reactants bound to the enzyme, the enzyme reaction will occur
up to 1014 times faster.
AMOUNTS AND CONCENTRATIONS
AMOUNT
CONCENTRATION
A quantity
A quantity/volume
mg, mole
M (mol/L), M
g, mol
mM, mg/mL
units
units/mL
Quantities such as milligrams (mg), micromoles (mol), and units
refer to amounts. Concentration is the amount per volume, so that
molar (M), micromolar (M), milligrams per milliliter (mg/ml), and
units per milliliter (units/ml) are concentrations. A unit is the
amount of enzyme that will catalyze the conversion of 1 mol of
substrate to product in 1