What are the requirements for an enzyme with Michaelis-Menten kinetics?

• Steady-state assumption: [ES] remains constant (loss
balances formation).
• [S] binds [E] to form [ES].
• Product formation is irreversible

What are the 3 ways of interpreting K_M

• Substrate concentration [S] at which at enzyme is at
half its maximum velocity Vmax (much like KD at half
ligand saturation).
• Approximation of the dissociation constant.
• The ratio of the rate constants:

k_-1+k₂/ k₁

What is a turnover number?

• Turn over number: kcat = Vmax/[E]total
The turnover number is a metric for the rate at which
substrate is converted to product (turnover) unique to
each enzyme.

What is the catalytic efficiency of an enzyme?

• Catalytic efficiency: kcat/KM
Catalytic efficiency scores an enzyme based on both its
affinity for substrate and rate of catalysis

Enzyme kinetics seeks to determine the initial and maximal reaction velocity that enzymes can

attain and the binding affinities for substrates and inhibitors

Michaelis-Menten equation has a ______line on a graph

non-linear

Bisubstrate reactions can occur by _____or______mechanisms or by a _______mechanism

ordered, random-sequential, Ping-pong

1st order reactions display a linear plot of the

substrate or product concentration, as a function of time

Rate law is the mathematical relationship

between the reaction rate or velocity, and concentration of reactions (linear)

The amount of A consumed per unit of time

rate, or velocity

Formula for rate law

v=k[A]^{number in front of letter}

Michaelis-Menten formula:

v_o=V_max[S]/ K_m+[S]

Vo is equal to

the slope

At low [S], the rate is proportional

as in a first-order reaction

At high [S], the enzyme reaction approaches

zero-order kinetics :V_o=V_max

Rate of formation of ES is _____, while rate of dissociation is ___.

Rate of product formation is ____

k₁, k_-1, k₂

Catalysis is limiting, because the rate is independent of [S](E is saturated

0^th order (when K_mis less than)

Rate is dependent on [S], [S] is limiting

1^st order (when K_m is greater than)

When above K_m, it starts to

plateau due to saturation increasing

V_max=k₂[E_T]

K_m=(k_-1+k₂)/k₁

Small K_m means

little dissociation (10^-6)

Larger K_m means

lots of dissociation (10^-2)

K_cat, the turnover number, is the number of

substrate molecules converted to product per enzyme molecules, per unit of time, when E is saturated with substrate

Catalytic efficiency formula:

k_cat/K_m

k_cat/K_m is approaching

1.0x10⁹

At temperatures are above 50^o to 60^oC,

enzymes typically decline in activity

The two classes of single-displacement:

random and ordered

Random single displacement where either

substrate may bind first, followed by the other substrate

Ordered single displacement where a

leading substrate binds first, followed by the other substrate

Double displacement (Ping-Pong) reactions

involves a covalent intermediate

In single displacement, high concentrations the

y-intercept is lower

Random, single-displacement reaction is formed rapidly and reversibly when

enzyme is added to a reaction mixture containing A,B,P, and Q

Ordered, single-displacement reaction leading substrate (A) must

bind first, followed by B. And for the products, P and Q

Double-displacement has a formation

of a covalently modified enzyme intermediate, E'

Reversible inhibitor may bind

at the active site or at some other site

Four types of reversible enzyme inhibitors:

-competitive

-noncompetitive

-mixed noncompetitive

-uncompetitive

Competitive inhibition

only time where inhibitor can be competed by the substrates

Increases the apparent K_m but

no effect on V_max

Noncompetitive inhibitor

decreases Vmax with no change in K_m

Mixed noncompetitive alters

both Km and Vmax

Uncompetitive inhibition alters

both Km and Vmax but with same slope Km/Vmax

Uncompetetive inhibition only observed

in enzyme having two or more substrates

What type of reversible inhibitor is this?

Competitive Inhibition

Competitive inhibition______apparent K_m but______on Vmax

increases, no effect

What type of reversible inhibitor is this?

Pure noncompetitive inhibition

Pure noncompetitive inhibition____Vmax with ____in Km

decreases, no change

What type of reversible inhibitor is this?

Mixed noncompetitive inhibition

Mixed noncompetitive inhibition alters Km and Vmax by _____

decreasing

What type of reversible inhibitor is this?

Uncompetitive inhibition

Uncompetitive inhibition alters both Km and Vmax but have ______

the same slope, Km/Vmax