Question

Biochemistry Chapter 6 : Vmax and Km

Estimation of and V_max and K_m by Inspection Although graphical methods are available for accurate determination of the V_max and K_m of an enzyme-catalyzed reaction (see Box 6-1), sometimes these quantities can be quickly estimated by inspecting values of V_0 at increasing [S]. Estimate the V_max and K_m of the enzyme-catalyzed reaction for which the following data were obtained.

Answer 1

The reaction of enzyme is given as follows: ES E+P E+S The Michaelis-Menten equation for this reaction is given as follows: 1 1 m Imax V max (1) (Ms VaMaximum Rate when all the of the substrate, i.e., Here, V Initial Rate : max k, [El: K (Ms), therefore, R, sucrose forms a complex (ES) with enzyme max Michaelis Menten's constant and Sucrose concentration (M). 0 1 1 follows the equation of line, i.e., ymx +c, where m slope The plot versus V K T1 and c intercept. On comparing equation (1) with the equation of line, m and V max 1 This plot is also known as Lineweaver-Burk plot C = V.

1/IS] 400000 35714.28571 1/Vo [S] 0.0000025 0.000028 Vo 0.000004 250000 0.00004 25000 100000 14285.71429 50000 10526.31579 25000 8928.571429 0.00001 0.00007 0.000020.000095 0.000040.000112 0.0001 0.000128 0.002 0.000139 10000 7812.5 500 7194.244604 100 7142.857143 0.01 0.00014 40000 y 7E-08x+ 0.0071 R2 1 35000 30000 25000 20000 15000 10000 5000 50000 150000 350000 400000 100000 200000 250000 300000 450000 1/S A/I

1 (M min) From graph, c-0.0071 from equation (1) Therefore, V 1 0.0071(Mmin) V K. m= Similarly, from graph, m7x10(min); from equation (1 = V Therefore, 1 K x V m= 7x10 (min K x 0.0071(/M min) 7x10 m K 0.0071(M mim 9.86x10 M 1 0.0071(Mmin 1 0.0071(/M min) -1 -140.845Mmin Hence, the Michaelis Menten's constant for invertase is K - 0.0412 M, and Vr is max 140.845 M min