Question

Which of the following affects the K_m? (There can be more than one answer)

a.   The enzyme concentration.

b.   The type of substrate.

c.   The substrate concentration.

d.   The temperature.

e.   The pH.

Answer 1

Ans) d , e

km is the Michaelis constant that corresponds to concentration of the substrate when velocity is half the maximum.

The factors that affect the km are;

• substrate concentration
• Effect of Temperature
• Effect of pH
• km does not vary with enzyme concentration because km is not dependent on enzyme concentration.It only describes the affinity of the enzyme to the substrate i.e if km value is high the enzyme has high affinity and minute amount of substrate will be required for the reaction.

Infact , when enzyme concentration is increased , the velocity of the reaction proportionately increases.

• Km value gives an approximate measure of concentration of substrate of the enzyme in that part of the cell  where reaction is occurring.

For eg. those enzymes which catalyse reactions with relatively more concentrated substrates (sucrose) usually have relatively high Km values and vice versa

• the km increases ,with increase in temperature
• pH can alter the binding affinity and the catalytic efficiency of the enzyme.