Peptide-Modulated Activity Enhancement of Acidic Protease Cathepsin E at Neutral pH

Table 1

Cathepsin-E-activating peptides and spacer peptides used for paired peptide library construction.

Name^1	Size (a.a.)	Amino acid sequence (N→C)	Activity (%)^2
S1	13	IEGRVGCDFMYVG	130
S2	8	GSPCIGII	133
S3	8	IVIHQQLL	—
S4	8	PGIKIIIIG	151
S5	9	IGPQFGMCG	—
S6	10	PGFEERSSEG	—
S7	16	SPIISHIVGCDPPSCG	160
S8	16	IGCEERSFPNIIIIIG	168
S9	13	SGIKVGCDPPSCG	140
S10	13	PGIKPPPCIIIIG	145
s1	10	GGGSGGGSGG	—
s2	10	GGGPGGGPGG	—
s3	15	GGGSGGGSGGGSGGG	—
s4	15	GGGPGGGPGGGPGGG	—

¹Cathepsin E-activating peptides (S1–S10) obtained from primary library selection [9] and spacer peptides (s1–s4) are shown.
²Activities were determined using peptides produced by the in vitro translation system (in italics) or chemical synthesis (in bold). Note that the former is less reliable than the latter and sometimes exhibits a higher activity than the latter and sometimes adversely systematically [19]. Cathepsin E activity alone was considered as to be 100%.