Table 1.

Inhibition of the proteasome subunits by the synthesised compounds.

Compd	R'	Xaa	R	IC50 (μm)aT-L	IC50 (μm)aChT-L	IC50 (μm)aPGPH
1	HMB	Leu	–(CH2)2−	77.44 ± 6.51	>100	1.21 ± 0.08
2	NBz	Leu	–(CH2)2−	65.32 ± 5.91	>100	2.35 ± 0.21
3	Bz	Leu	–(CH2)2−	58.43 ± 5.13	>100	2.61 ± 0.23
4	1-NaftCO	Leu	–(CH2)2−	21.08 ± 1.85	0.82 ± 0.08	0.91 ± 0.07
5	HMB	Asn	–(CH2)2−	68.35 ± 5.14	8.47 ± 0.75	6.18 ± 0.55
6	NBz	Asn	–(CH2)2−	17.23 ± 1.09	0.92 ± 0.09	1.19 ± 0.13
7	Bz	Asn	–(CH2)2−	49.66 ± 3.87	7.99 ± 0.67	11.23 ± 0.98
8	1-NaftCO	Asn	–(CH2)2−	35.23 ± 2.77	76.25 ± 6.82	10.01 ± 1.27
9	HMB	Phe	–(CH2)2−	>100	0.85 ± 0.07	0.88 ± 0.08
10	NBz	Phe	–(CH2)2−	35.40 ± 2.91	0.77 ± 0.06	0.24 ± 0.3
11	Bz	Phe	–(CH2)2−	53.18 ± 6.70	6.22 ± 0.48	1.05 ± 0.09
12	1-NaftCO	Phe	–(CH2)2−	49.75 ± 3.97	9.14 ± 1.02	35.76 ± 4.03
13	HMB	Ser	–(CH2)2−	>100	>100	91.52 ± 7.69
14	NBz	Ser	–(CH2)2−	63.36 ± 7.01	83.47 ± 8.03	78.66 ± 8.14
15	Bz	Ser	–(CH2)2−	53.82 ± 4.88	24.11 ± 1.98	5.78 ± 4.35
16	1-NaftCO	Ser	–(CH2)2−	>100	>100	>100
17	HMB	Leu	–(CH2)4−	>100	11.50 ± 1.02	7.82 ± 0.71
18	NBz	Leu	–(CH2)4−	>100	8.40 ± 0.72	10.54 ± 0.82
19	Bz	Leu	–(CH2)4−	>100	10.12 ± 0.70	2.41 ± 0.14
20	1-NaftCO	Leu	–(CH2)4−	>100	49.30 ± 5.02	45.35 ± 4.03
21	HMB	Asn	–(CH2)4−	>100	65.38 ± 6.50	9.52 ± 1.09
22	NBz	Asn	–(CH2)4−	>100	28.52 ± 3.05	>100
23	Bz	Asn	–(CH2)4−	>100	24.19 ± 2.05	>100
24	1-NaftCO	Asn	–(CH2)4−	>100	78.34 ± 6.95	>100
25	HMB	Phe	–(CH2)4−	>100	17.50 ± 1.07	8.82 ± 0.71
26	NBz	Phe	–(CH2)4−	>100	9.10 ± 0.6	10.54 ± 0.82
27	Bz	Phe	–(CH2)4−	>100	10.12 ± 0.70	5.43 ± 0.44
28	1-NaftCO	Phe	–(CH2)4−	79.71 ± 6.97	9.30 ± 1.02	25.65 ± 3.03
29	HMB	Ser	–(CH2)4−	80.24 ± 6.91	45.68 ± 2.59	61.52 ± 4.99
30	NBz	Ser	–(CH2)4−	83.26 ± 7.21	88.74 ± 8.03	83.66 ± 8.16
31	Bz	Ser	–(CH2)4−	>100	84.11 ± 6.08	3.55 ± 1.65
32	1-NaftCO	Ser	–(CH2)4−	60.75 ± 4.88	>100	83.62 ± 5.48
33	HMB	Leu	–cHx-	>100	>100	>100
34	NBz	Leu	–cHx-	>100	42.10 ± 5.02	>100
35	Bz	Leu	–cHx-	>100	23.12 ± 1.70	>100
36	1-NaftCO	Leu	–cHx-	>100	59.30 ± 6.42	73.67 ± 1.45
37	HMB	Asn	–cHx-	>100	>100	>100
38	NBz	Asn	–cHx-	>100	>100	>100
39	Bz	Asn	–cHx-	>100	>100	>100
40	1-NaftCO	Asn	–cHx-	>100	>100	>100
41	HMB	Phe	–cHx-	>100	>100	>100
42	NBz	Phe	–cHx-	>100	82.10 ± 6.52	>100
43	Bz	Phe	–cHx-	>100	73.31 ± 3.90	>100
44	1-NaftCO	Phe	–cHx-	>100	>100	83.37 ± 4.58
45	HMB	Ser	–cHx-	>100	>100	>100
46	NBz	Ser	–cHx-	>100	>100	5.78 ± 0.62
47	Bz	Ser	–cHx-	>100	>100	3.42 ± 0.51
48	1-NaftCO	Ser	–cHx-	>100	>100	11.71 ± 1.25
MG132				1.04 ± 0.092	0.0018 ± 0.00022	>10

^aThe values reported are the mean ± SEM of three independent determinations.