SFP7: Enzyme Kinetics Flashcards
Does an enzyme affect the kinetics or equilibrium of a reaction?
The kinetics of a reaction (NOT the equilibrium)
What is V0?
Initial velocity when substrate is added to reaction mixture
Describe the method of analysing the kinetics of enzyme catalysed reactions?
Collect data at constant enzyme concentration, several different [S], calculate initial rate (Vo) and plot Vo against [S]
What is the dependence of Vo on [S] known as?
Hyperbolic
What is Vmax?
Maximum velocity catalysed by a given enzyme concentration
What is Km?
The [S] which gives 1/2 Vmax
When [S]=Km, what does V0 equal?
V0= Vmax/2
What is the equation that relates Vo to Vmax and Km?
Vo= Vmax x ([S] / ([S] + Km))
What is the equation called that relates Vo to Vmax and Km?
Michaelis-menten equation
What units does Km have?
Concentration units
What information does the michaelis constant give (Km)?
The affinity of an enzyme for its substrate
What does high Km mean?
Relatively weak substrate binding
Explain the example of alcohol metabolism with importance of Km?
most people produce a low Km (high affinity) aldehyde dehydrogenase to break down acetaldehyde efficiently
However some people produce a high Km (low affinity) form of aldehyde dehydrogenase , leads to facial flushing and tachycardia
What is the kCat?
A turnover number or molecular activity (molecules of substrate transformed per unit time (usually given as per second))
What value(s) are useful for comparing two enzymes?
The enzyme turnover number (KCat), is a good indicator of efficiency
