Question

Isocitrate lyase catalyzes the following reaction: isocitrate ion → glyoxylate ion + succinate ion.

The rate, v, of the reaction was measured when various concentrations of isocitrate ion were present, and the following results were obtained at 25C:

[isocitrate]/(umol dm−3) 31.8 46.4 59.3 118.5 222.2

V/(pmol dm−3 s−1) 70.0 97.2 116.7 159.2 194.5

Determine the Michaelis constant and the maximum velocity of the reaction.

Answer 1

We will plot a graph here between 1/[S] and 1/V

[S] = concentration of isocitrate

V = rate of reaction

[S]	1/[S]	V	1/V
31.8	0.031447	70	0.014286
46.4	0.021552	97.2	0.010288
59.3	0.016863	116.7	0.008569
118.5	0.008439	159.2	0.006281
222.2	0.0045	194.5	0.005141

The plot will be

For this equation we obtain a plot

y = 0.335x + 0.003

1/Vmax = intercept = 0.003

Vmax = 333.33

Km / Vmax = Slope

Km = Slope X Vmax = 0.335 X 333.33 = 111.65