Table 1.

Kinetic inhibition of the three primary protease activities of the 20S proteasome by Z-specific inhibitors

Inhibitor	kobs/[I] (1/M)
	Suc-LLVY-MCA	Boc-LRR-MCA	Z-LLE-MCA
Ac-PRLN-VS	ND	1,572  ± 3 (0.2–2 μM)	ND
Ac-YRLN-VS	ND	1,530  ± 1 (0.2–5 μM)	ND
Ac-PKLN-VS	ND	584  ± 3 (0.5–10 μM)	ND
Ac-YKLN-VS	ND	456  ± 2 (0.5–10 μM)	ND
Ac-PRKN-VS	ND	2,149  ± 4 (0.5–5 μM)	ND
Ac-YRKN-VS	5.4 ± 0.4 (100–500 μM)	1,442  ± 7 (1–5 μM)	13.9 ± 0.5 (100–500 μM)

ND indicates no inhibition of substrate hydrolysis was observed at concentrations as high as 100 μM.