TABLE 2.

Substrate sensitivity to protease II

Substrate	Optical density at 30 mina	Enzyme activityb
N-Acetyl-Ile-Glu-Ala-Arg-pNA	0	0
N-Benzoyl-Pro-Phe-Arg-pNA hydrochloride	0	0
Nα-Benzoyl-l-arginine-pNA hydrochloride	0	0
N-Benzoyl-Phe-Val-Arg-pNA hydrochloride	0	0
N-CBZ-Gly-Gly-Leu-pNA	0	0
d-Ile-Phe-Lys-pNA	0	0
N-Succinyl-Gly-Gly-Phe-pNA	0	0
N-Tosyl-Gly-Pro-Arg-pNA	0.197	1.10
dl-Val-Leu-Arg-pNA	0.416	1.47
N-Succinyl-Ala-Ala-Pro-Phe-pNA	0	0

^aReactions were started with the addition of protease II to buffer and substrate. The reaction mixture was immediately placed into a microtiter plate reader, where the optical density at 410 nm was read at 5-min intervals for 30 min and the units of enzyme were calculated from the change in optical density (ΔA) per minute.

^bOne unit of protease II activity was defined as ΔA/min × total assay volume/sample volume × E at 410 nm × light path (cm), where the extinction coefficient (E) of the product (paranitroanilide) at 410 nm was 9.75 and the light path was 0.53 cm (26).