FIG. 4.

Effects of nPP on the activities of vEP and thermolysin. (A) Protease activities of vEP and thermolysin (TLN) in the absence or presence of different [nPP]/[E] ratios. The enzyme (100 nM) was preincubated with different concentrations of nPP at 37°C for 10 min, and residual activity was measured following the addition of prewarmed azocasein as a substrate. Protease activity was measured with a final enzyme concentration of 80 nM. Residual protease activities of samples containing nPP were expressed as a percentage of the activity of the sample without nPP. Data are means ± standard deviations from two experiments carried out in triplicate. (B) SDS-PAGE of vEP and thermolysin preincubated with different concentrations of nPP. The enzyme (5 μg) was incubated without or with different amounts of nPP ([nPP]/[E] ratios of 1 and 4) in a 15-μl sample volume at 37°C for 10 min and then subjected to SDS-PAGE using a 12% gel. The final enzyme concentrations were 7.4 μM (vEP-45), 9.8 μM (vEP-34), and 9.7 μM (TLN). E, enzyme only.