Carbonic anhydrase catalyzes the reaction H_20(l) + C0_2 (g) H_2CO_3 (aq). Data
ID: 1072474 • Letter: C
Question
Carbonic anhydrase catalyzes the reaction H_20(l) + C0_2 (g) H_2CO_3 (aq). Data for the reverse dehydration reaction using a total enzyme concentration of 2.32 times 10^-9 M are given below Determine the values of K_m, the Michaelis constant, and k_2, the rate if product formation from the enzyme substrate complex. The protein catalase catalyzes the reaction 2H_20_2(aq) rightarrow 2H_2O (l) + O_2(g) and has a Michaelis constant of K_m = 25 times 10^-3 M, and a turnover number of 4.0 times 10^7 s^-1. Calculate the initial rate of this reaction if the total enzyme concentration is 0.016 times 10^-9 M and the initial substrate concentration is 4.32 times 10^-6 M. Calculate V_max for this enzyme. Catalase has a single active site.Explanation / Answer
From V=Vmax*S/ (KM+S)
1/V = (KM/Vmax)*1/S + 1/Vmax
the plot of 1/V vs 1/S gives a straight line whose slope is K/mVmax and intercept is 1/Vmax
the plot of 1/V vs 1/S is drawn and is shown below
the intercept is 1/Vmax = 12554, Vmax= 1/12554 =7.9*10-5 M/s
KM/Vmax = 2*108, KM= 15931M
but Vmax= K2[E]
7.9*10-5 = K2(2.32*10-9)=79666 M/s
2. turn over number = Vmax/[E]
Vmax= 4*107*0.016*10-9 =0.00064 M/s
V= VmaxS /(KM+S)
(-dS/dt) = VmaxS/(KM+S)
-(dS/dt) t= 0 = Vmax*SO/ (KM+SO) = 0.00064*4.32*10-6/ (25*10-3+4.32*10-6)=1.105*10-7 M/s