Enzyme Kinetics

Front 1

differences between enzyme catalyzed and uncatalyzed rxns

Back 1

1. catalysis reaches saturation

2. enzymes reduce the activation energy

Front 2

Reaction Order

Back 2

refers to the number of molecules that need to interact

Front 3

Vmax

Back 3

theoretical maximum velocity of the rxn

Front 4

Km

Back 4

[S] at which half the maximal velocity is achieved. Includes the affinity of the enzyme for the substrate and the rate of conversion of ES to E+P

Front 5

Differences between steady state and equilibrium

Back 5

1. there is only one equilibrium point (when ∆G=0)
2. steady state concentrations of S and P vary depending upon the rates of formation and degredation
3. at equilibrium [S] and [P] are INdependent of [E]
4. Steady State levels are determined by the activities of enzymes that form/degrade reactants and products.

Front 6

steady state assumption

Back 6

[ES] is constant over time
[S]>>>>[E]

Front 7

Michaelis-Menton Equation

Back 7

v₀=Vmax*[S]/{Km+[S]}

Front 8

kcat

Back 8

turnover number or catalytic constant. rate of ES→E+P. the number of reactions that an enzyme preforms per second.

Front 9

catalytic efficiency

Back 9

kcat/Km

Front 10

Back 10

Lineweaver-burke plot

Front 11

Back 11

-1/Km

Front 12

Back 12

1/[S]

Front 13

Back 13

1/v

Front 14

Back 14

1/Vmax

Front 15

Back 15

Km/Vmax

Front 16

Back 16

Eadie-Hofstee Plot

Front 17

Back 17

Competitive Inhibitor

Front 18

Back 18

Noncompetitive Inhibitor

Front 19

Back 19

-Km

Front 20

Back 20

v0

Front 21

Back 21

v0/[S]

Front 22

Back 22

Vmax

Front 23

Back 23

Vmax/Km

Front 24

Factors that effect enzymes

Back 24

pH

ionic strength

temperature

inhibitors

Front 25

Competitive inhibtion

Back 25

inhibitor binds reversibly to the same site as the substrate

Vmax is unchanged

Km changes with [I]

Front 26

Mixed (noncompetitive) inhibition

Back 26

inhibitor binds both E and ES

Vmax changes with [I]

Km remains constant

does not affect of substrate binding

Front 27

sequential bisubstrate reaction

Back 27

both substrates first bind E then products are released. can be ordered or random.

Front 28

ping-pong bisubstrate reaction

Back 28

the product of the first substrate is released before the second substrate binds. necessitates a modified enzyme intermediate.

Front 29

oligomeric allosteric enzymes

Back 29

binding ligand by one subunit makes it easier for others to bind (cooperativity). these don't follow michaelis-menten; they have sigmoidal graphs.

Front 30

the hill equation

Back 30

log[v/(Vmax-v)]=n*log[S]-logK'

n=index of cooperativity=hill coefficient

Front 31

Kd

Back 31

Measure of affinity of the ligand for the protein

1/Ka=[L][P]/[LP]