2020 Enzyme Engineering / Problem set #4       Due date: May 28, pm 5:00

※ Solve the following problems (clearly indicate unit in your answers).

1. An enzyme-catalyzed reaction was found to be affected by an inhibitor.

The following results were obtained at fixed total enzyme concentration.

What is the degree of inhibition (%) in this reaction?

Substrate concentration (mM)	Initial reaction velocity (mmol/l․min)
	Uninhibited	With 0.5 mM inhibitor
2	0.55	0.25
2.5	0.66	0.30
3.3	0.80	0.36
5	1.02	0.47
10	1.43	0.65

2. Two sets of enzyme reactions were carried out and data were given below (Vo: initial reaction velocity in the absence of inhibitor, VI: initial reaction velocity in the presence of inhibitor). What is the degree of inhibition in each reaction?

S (mM)	Vo (μM/min): No inhibitor	VI (μM/min) by 1 mM inhibior A	VI (μM/min) by 10 mM inhibior B
0	0	0	0
1	21	16	11
2	34	26	20
5	56	43	37
10	70	54	54
100	92	70	88

3. An enzyme has a Km of 4.7x10-5 M. If the Vmax of the preparation is 22

μmoles/liter‧min, what velocity (vi) would be observed in the presence of 2x10-4 M substrate and 5 x10-4 M of (a) a competitive inhibitor, (b) a noncompetitive inhibitor, (c) an uncompetitive inhibitor. Ki in all three cases is 3x10-4 M.

(d) What is the degree of inhibition in all three cases?