Table II. Effect of proteasome inhibitors on the digestion of the 31-mer substrate.

	No Inhibitor	MG-132	Epoxomicin
Amount digested	100%	28.9%	54.3%
N. of digestion products	80	28	16
Peptides involving dual cleavagea	66 (82.5%)	20 (71.4%)	7 (43.8%)
N. of cleaved peptide bondsb	29 (96.7%)	22 (73.3%)	19 (63.3%)
N. of productive species for the A68 ligandc	4 (5.1%)	2 (7.1%)	1 (6.3%)
Relative yield of productive cleavagesd	6.9%	5.5%	2.6%
N. of destructive cleavages for the A68 ligande	10 (34.5%)	8 (36.4%)	4 (21.1%)
Relative yield of the destructive cleavagesd	20.3%	26.3%	7.8%
N. of productive species for the B27 ligandc	12 (15.2%)	2 (7.1%)	2 (12.5%)
Relative yield of productive cleavagesd	28.2%	14.6%	17.0%
N. of destructive cleavages for the B27 ligande	9 (31%)	6 (27.3%)	7 (36.8%)
Relative yield of the destructive cleavagesd	25.9%	18.3%	45.8%
Destruction/production ratio for the A68 ligandf	2.9	4.8	3.0
Destruction/production ratio for the B27 ligandf	0.9	1.3	2.7

^a Percent relative to the total number of digestion products.

^b Percent relative to the total number of peptide bonds in the substrate.

^c Peptides with the right C-terminus and right or extended N-terminus. Percent values are relative to the total number of digestion products (see Table VS).

^d Added values from Table VIS. For productive cleavages the yields correspond to the relative contribution of cleavage after R17 or Y25 for the A68 and B27 ligands, respectively.

^e Cleaved peptide bonds implying destruction of the epitope. Percent values are relative to the total number of cleaved peptide bonds.

^f Ratio between the joint relative yield of cleavages implying destruction of the natural ligand and that of the potentially productive peptides.