Question

The following parameter(s) of an enzyme-catalyzed reaction depend(s) on enzyme concentration:

A) Km (Michaelis constant)

B) Vmax (maximum velocity)

C) kcat (turnover number)

D) A and B

E) B and C

Km is the equivalent of:

A) Substrate concentration at Vo

B) Substrate concentration when Vmax is reached

C) Substrate concentration when 1/2 Vmax is reached

D) Product concentration when 1/2 Vmax is reached

Answer 1

The answer to first question is option E. (Both V_max and Turnover Number ) are dependent on enzyme concentration.
    ( k_cat=V_max/E )
Both V_max and k_cat are dependent on E.

K_m can change with enzyme concentration if say the enzyme is oligomeric ( not in case of monomeric enzyme)

K_m or the Michaelis-Menten constant tells us about the concentration of the substrate when the reaction velocity is equal to half of V_max ( maximal velocity ) for the reaction.

When we put V₀=V/2 , The concentration of Substrate is equal to Km.
Thus C is the correct option for 2nd question.