Enzyme kinetics Flashcards
What is enzyme kinetic?
Discipline focused on determining the rate of reaction and how it changes in response to changes in experimental parameters
What is the rate enzymatic reaction affected by?
Enzyme
Substrate
Effectors
Temperature
What is Kcat?
Enzyme turnover number
Number of times each enzyme site converts substrate to product per unit time
What does the Kcat describe?
The number of times each enzyme site converts substrate to product per unit time for a given enzymes concentration
What is Km
Concentration at 1/2 Vmax
What does Km tell you?
Affinity
Low Km high affinity
High Km low affinity
How do you measure efficiency of an enzyme?
Kcat/Km
How are affinity and specificity related?
More specific higher affinity
2 types of substrate reactions when 2 or more reactants are involved
Sequential reactions
Double displacement reactions
2 ways of sequential reactions
Random or ordered
Different name for double replacement reaction
Ping-pong
Different name for irreversible inhibitors
Inactivators
What can reversible inhibitors bind to?
Free enzyme (prevent binding of substrate)
Enzyme-substrate complex (prevent reaction)
What are reversible inhibitors often?
Structural analogs of substrates or product
Are irreversible inhibitors competitive?
No
How is the velocity of an enzymatic reaction calculated?
Measuring the quantity of substrate transformed per unit time or products formed by the reaction
Which inhibitors are competitive?
Reversible
What can you measure the formation of product with when mixing an enzyme and substrate?
Spectrophotometer
What is the affinity with the enzyme when the Km is low?
High, need less substrate to get to 1/2 Vmax
What is the affinity with the enzyme when the Km is high?
Low, need more substrate to get to 1/2 Vmax
What does a high ratio between Kcat and Km say about the efficiency?
High efficiency
Is high efficiency of an enzyme always a good thing?
No it depends on the enzyme and it’s function
What can a non-linear Michaelis-Meenten plot be used to calculate?
Km and Vmax
What is the slope in a Lineweaver-burk plot?
Km/Vmax
What is Km used as a measure of?
An Enzyme’s affinity for its substrate
What happens to Vmax when enzyme concentration is doubled?
It is also doubled
What happens to Km when enzyme concentration is doubled?
Remains the same, is independent of enzyme concentration
What does the lineweaver-burk plot?
The Michaelis Menten equation
2 possible scenarios when having a 2 substrate reaction
Sequential reaction
Double displacement reactions
What is a sequential reaction?
Reaction where an enzyme reacts with another enzyme before reaction with a second substrate which then forms product
What is a double displacement reaction?
Also called ping-pong reaction because substrates bind sequentially
Are sequential reactions random or ordered?
Can be both
Which substrate binds first in an ordered sequential reaction?
The leading substrate
Which substrate binds first in a random sequential reaction?
Either of the substrates may bind first
