Table 1.

Inhibition of proteasome catalytic activities

Compound	kassociation = kobs/[I] (M−1s−1)
	Chymotrypsin-like activity	Trypsin-like activity	PGPH activity
Epoxomicin	35,400  ±  1400	287  ±  71	34  ±  4.8
	(40–80 nM)	(6–10 μM)	(25–75 μM)
clasto-lactacystin	8,530  ±  280	253  ±  41	37  ±  4.7
β-Lactone	(200–400 nM)	(6–10 μM)	(25–75 μM)
NLVS	6,790  ±  919	5.3  ±  2.8	6.4  ±  2.3
	(200–400 nM)	(50–100 μM)	(50–100 μM)

The rate of covalent inhibition (k_association) of the three major proteasome catalytic activities were determined for epoxomicin, clasto-lactacystin β-lactone, and peptide vinyl sulfone, NLVS. A range of concentrations was used to determine the k_association for inhibition of individual enzymatic activities.