Table 3. The effects of mixtures of PDPA and ZD9331 on hTS activity.

The effects of mixtures of PDPA and ZD9331 on hTS activity. Measured values, relative to the maximum velocity, are given in Obs columns. Theoretical activities, V_1,2, calculated with equation 1 that predicts reaction velocities for a mixture of non-interacting inhibitors are in Calc columns. The bottom row contains ratios of V_calc/V_obs. The deviations from expected values may be considered a measure of inhibitors cooperativity (24).

Constant [ZD9331]
10 nM PDPA 10 nM ZD9331		100 nM PDPA 10 nM ZD9331		250 nM PDPA 10 nM ZD9331		1 μM PDPA 10 nM ZD9331		2 μM PDPA 10 nM ZD9331		10 μM PDPA 10 nM ZD9331
Calc.	Obs.	Calc.	Obs.	Calc.	Obs.	Calc.	Obs.	Calc.	Obs.	Calc.	Obs.
54.7	42.6	53.3	29.5	49.75	23.8	44.09	18.1	43.67	17.2	37.77	16.1
1.28		1.81		2.09		2.44		2.54		2.35
Constant [PDPA]
1 nM ZD9331 1 μM PDPA				10 nM ZD9331 1 μM PDPA		100 nM ZD9331 1 μM PDPA		1 mM ZD9331 1 μM PDPA		10 mM ZD9331 1 μM PDPA
Calc.		Obs.		Calc.	Obs.	Calc.	Obs.	Calc.	Obs.	Calc.	Obs.
71.6		27.3		54.9	17.9	31.7	15.1	12.1	12.1	7.3	6.9
2.09				1.00		2.62		3.06		1.06