Table 1

Inhibition effects of PDE3-selective inhibitors on PDE3A mutants

	K_i
	Cilostazol	Milrinone	cGMP	K_m cAMP	Catalytic Efficiency K_cat/K_m
	μM		μM/s
PDE3A	0.57 ± 0.11	0.66 ± 0.12	0.76 ± 0.09	0.21 ± 0.02	8.58
Y751A	10.4 ± 3.45	7.45 ± 1.06	6.71 ± 0.60	0.53 ± 0.03	0.20
T844A	14.2 ± 3.29	1.31 ± 0.11	0.46 ± 0.10	0.35 ± 0.02	1.29
N845A	0.77 ± 0.16	0.90 ± 0.26	0.88 ± 0.06	0.92 ± 0.26	1.58
L910A	0.64 ± 0.08	1.89 ± 0.41	1.72 ± 0.15	0.50 ± 0.07	0.59
D950A	12.1 ± 1.20	12.2 ± 1.83	40.1 ± 2.26	0.23 ± 0.01	0.08
F972A	10.4 ± 0.83	1.67 ± 0.16	1.67 ± 0.07	0.65 ± 0.10	0.56
Q975A	7.23 ± 1.57	0.77 ± 0.06	0.24 ± 0.02	0.24 ± 0.05	0.88
F1004A	212 ± 10.6	156 ± 15.5	>100	27.2 ± 0.61	0.03

The mutants are listed in order of their position in the sequence. All determinations represent the mean ± S.D. of at least three separate experiments. The bold values are elevated 3-fold compared with recombinant PDE3A. Differences are statistically significantly (P < 0.001) using Student's t-test. Values for cGMP K _i, cAMP K _m, and catalytic efficiency are from Zhang et al. (2001).