TABLE 1.

Effects of protease inhibitors on EhCP activitya

InhibitorSpecificity of inhibition% Residual activityb
CystatinCysteine2 ± 0.79
E-64Cysteine5 ± 0.54
LeupeptinCysteine/serine5 ± 0.43
TLCKCysteine/serine2 ± 0.25
TPCKcCysteine/serine6 ± 1.49
Pefabloc SCSerine93 ± 1.43
AprotininSerine100 ± 2.51
PepstatinAspartic acid100 ± 7.57
PhosphoramidonMetallo-100 ± 1.00
  • a EhCP activity was measured using the synthetic substrate Z-Arg-Arg-pNA. CPs cleave substrates with arginine in the P-2 position. SPs typically contained between 8 and 13 U of activity per μg of protein, and in this study, 50 μg of protein with a total of 630 U was used.

  • b Mean percent residual activity (of control) ± SD (n = 3).

  • c TPCK, tosylsulfonyl phenylalanyl chloromethyl ketone.