Table 2. Cathepsin L, Cathepsin V, PC1/3, and PC2 Cleavage of Peptide-AMC Substrates with Variant Dibasic Residues, without and with Cathepsin H Aminopeptidase Activity to Assess Processing Sites^a.

	ratio of protease activity ± cathepsin H (RFU fluorescence)
substrate	cathepsin L	cathepsin V	PC1/3	PC2
Z-K-R-AMC	1.5	202.4	infinity, CH only	2.6
Z-R-K-AMC	1.0	1.0	1.0	0.9
Z-K-K-AMC	1.1	1.4	3.0	0.8
Z-R-R-AMC	1.1	6.8	infinity, CH only	1.5
Z-L-K-R-AMC	infinity, CH only	infinity, CH only	0.9	0.1
Z-W-K-R-AMC	73.9	48.3	0.9	1.3
Z-F-K-R-AMC	infinity, CH only	infinity, CH only	1.1	1.4
Z-Y-K-R-AMC	infinity, CH only	269	0.9	1.0
Z-V-K-R-AMC	29.7	infinity, CH only	2.9	0.7
Z-G-K-R-AMC	infinity, CH only	2.8	infinity, CH only	0.3
Z-A-K-R-AMC	26.1	infinity, CH only	1.9	1.2

^aThe ratio of each protease activity was assessed in the absence and presence of cathepsin H in coupled assays to monitor cleavages at the C-terminal side of dibasic residues compared to cleavages occurring between or at the N-terminal side of dibasic residues. The ratio of activity, indicated by the relative fluorescence of free AMC, in the presence and absence of cathepsin H is shown in this table. When AMC fluorescence was generated only in the presence of cathepsin H (CH), the table indicates “infinity, with CH only.” The ratios of proteolytic activity ± cathepsin H represent data from Figures 5 and 6.