Table 2. Inhibition Constants of Dipeptide Nitriles with Varying P1 Side Chains for Cathepsins B, S, L, and K^a.

	Ki (μM)
	56a	1b	35a	35b	35c	42	43
CatB	1.19(4)	0.042(3)	4.1(1)	4.6(5)	2.34(8)	0.86(3)	1.61(4)
CatS	0.055(5)	0.044(4)	0.279(7)	0.32(2)	0.21(1)	0.110(9)	0.191(2)
CatL	0.049(3)	0.220(4)	0.69(2)	0.54(3)	0.47(2)	0.049(2)	0.52(2)
CatK	2.1(2)	8.8(2)	30(5)	25(2)	26(2)	4.0(1)	19.1(6)

^aData shown are mean values ± SEM of three experiments, each performed in duplicate.