. Author manuscript; available in PMC: 2014 Aug 8.

Published in final edited form as: J Med Chem. 2013 Jul 22;56(15):6054–6068. doi: 10.1021/jm4006719

Table 2.

Detailed inhibition constants for Cal1 and papain and relative inhibitor selectivity.^a

	Calpain1				Papain				10² × k_i/K_i Call k_i/K_i papain	Relative selectivity compared to E-64^c

	K_i (μM)	k_i (s⁻¹)	k_i/K_i^a ×l0⁻⁴ s⁻¹M⁻¹	re1^b	K_i (μM)	k_i (s⁻¹)	k_i/K_i^a ×l0⁻⁴s⁻¹M⁻¹	re1^b
E-64	3.96	0.12	3.02±0.15	1	5.08	28.6	563 ± 52	1	0.54	1
22a	6.02	0.16	2.74±0.19	0.91	1.62	17.1	1,050 ±41	1.9	0.26	0.5
31	2.59	0.08	2.96±0.14	0.98	5.31	14.8	279 ± 47	0.50	1.06	2.0
32	3.53	0.14	3.89±0.41	1.3	9.70	21.6	223 ± 2.4	0.40	1.74	3.3
36	2.89	0.10	3.31±0.32	1.1	19.2	12.7	66.2 ±7.4	0.12	5.0	9.3

Calculated inhibition rate and apparent equilibrium constants versus full length Call and papain.

k_i/K_i calculated relative to E-64.

Selectivity calculated using k_i/K_i relative to E-64 set at 1.0. Inhibition constants were calculated as described in the text, varying both enzyme and inhibitor concentrations. Data represent the mean ± S.D. of triplicate experiments.