Enzymes - Michaelis-Menten Kinetics Flashcards
Enzyme Kinetics
This is the study of understanding rate of reaction and how it changes to various experimental parameters
What may complicate enzyme kinetics?
Substrate concentrations changes during reaction in converstion to the product
How can substrate change be determined?
Initial Rate V0
What is the state of the substance at inital rate?
Enzyme is in nanomolar quantities whilst subtrate on 5-6 orders of amgnitude.
How can [S] be limited to few precent?
If only hte begining of the reaction is monitred.
What can inital rate be used to study
Inital rate as a funciton of [S] : at low substrate concentraitons, V0 increases near linearly with increasing [S]
Maximum Velocity
This is where all enzymes at maximum spped at high substrate concentration
How is ES complex formation described?
E + S <–>ES
What are the two steps of a reaction?
E+S,<->ES
ES<–> E+P
What does ES<–>E+P describe?
Complex break down forming enzyme and reaction product
What do ES and E concentration differ depend on?
S concnetratnion, at low most enzyme in E form, where rate of activity is proportional to S as equilibrium favours more ES formaiton with S increase
When does maximum velocity occur?
When al enzymes present are in ES complex formation, where further S increase does not affect rate due to enzyme saturation
What is important to note when P is formed?
E is able to form ES again to catalyse another reaciton.
Pre-Steady State
This occurs when there is a rapid burst of ES complexes forming in the beginning the process is slow because the ES is still forming, then it increases
What does S and V0 relationship approach?
Rectangular hyperbola
What does the MMK express?
Relationship between S and V0
Michaelis-Menten Kinetics
This estimates enzyme kinetic parameters from reaction progress curves of substrates
What is the MMK Equation?
V0=Vmax[S]/Km+[S]
Michaelis Constant
This is as substrate concentration at which the rate of reaciton is half the maximum rate that can be achived under given conditions, that being where velocity of reaction is half Vmax
What was MMK derivation initally base don?
Idea that enzymatic reactons rate limiting step is ES complxe breakdown to E
What does KM describe?
Michaelis Constant
What is the units of Km?
nmol L^-1
Initial Velocity
This is the rate at which the reaciton proceeds at a given substrate concentraiton
What is inital velocity determined by?
ES breakdown to form product: V0=K2[ES]
What does Et represent?
Total enzyme content, whether E or ES, where E equals Et-ES
What is ES formation rates govered by?
K1
What is ES breakdown rate foverned by?
k-1+k2
Steady-State Assumption
This is the concentraiton of the intermediates of a reaction remain the same even when the concentraiton of starting materials and products are hcanging
What is the steady state assumption given by?
K1[ET]-[ES]))[S]=k-1[ES]+k2[ES]
What does the MM equation descrie?
The rate equation for a one-ubstrate enzyme-catalysed reaction, relating inital velocity, maximum velocity and inital substrate concentraiton with the michaelis constant.
How do enzymes realte to MMK?
Most follow MM kinetics, except regulatory enzymes, hoever some exhibiting beyond the two steps can follow these kinetics
What are the assumption s of MM kinetics?
Reaction is assumed to be a single substrate reaction(inhibition concentraiton)#K2 assumes no reverse mechanism is present, like product inhibition or reverse catalysis.
What is the doubling relationship between S and B?
When KM is 100nML^-1 and [S] are 1 and 2, Vmax being constant, then
Vmax[1]/100+[1]
Vmax[2]/100+[2]
When is Vmax constant?
If [E] is the same
Why does MM form a rectnagular hyperbola?
Initial linear increase limited when S<Et
Parabolic with increasing [S] and [E] saturation
