Enzymes

Kinetics, Inhibtors

Known conditions needed for experimmental assays

Buffer, substrate conc., temp, enzyme conc.

ES association constant

K_A = [ES] / [E][S] | (k₁/k_-1)

ES dissociation complex

K_D = 1/K_A = [E][S] / [ES] | (k_-1/k₁)

V₀ (Initial Velocity)

Earliest speed of k₂

V_max

When [S] is saturated (high [S]) —> =V₀

Michaelis complex

ES

Steady state (Michaelis Menten)

When [ES] and [E] do not change

Transient Phase (Michaelis Menten)

Very fast step before steady state

Michaelis Constant

K_{M :} K_M= [S] at ½ of V_max

K_M

Estimate of substrate binding affinity

Michaelis-Menten Equation

Specificity constant

k_cat/K_M

Specificity constant definition

Measure of substrate preference/catalytic efficiency

M^-1s^-1

Specificity constant units

Larger value for great enzyme relative to poor enzyme

Specificity constant trend

Catalytic Proficiency

Measure of an enzyme’s affinity for transition state

Lineweaver-Burke

Double reciprocal plot

Slope (m) : K_M/V_max

Y-intercept (b) : 1/V_max

X-intercept: -1/K_M

Lineweaver-Burke Plot parameters

Irreversible inhibition

Enzyme permanently destroyed (covalent)

Reversible inhibition

Enzyme not destroyed-can be reactivated upon removal of inhibitor

Competitive, uncompetitive, non-competitive

3 forms of reversible inhibitors