New Insights on Plasmin Long Term Stability and the Mechanism of Its Activity Inhibition Analyzed by Quartz Crystal Microbalance

We used the research quartz crystal microbalance (RQCM) to monitor regulatory effects of plasmin and trypsin in the presence of their inhibitor alpha(2)-antiplasmin. The gold surface of quartz crystals was modified with a beta-casein layer that served as a substrate for protease digestion. The addition of plasmin or trypsin as well as their mixtures with alpha(2)-antiplasmin resulted in an increase of resonant frequency, f, and in a decrease of motional resistance, R-m, depending on the molar ratio of protease: antiplasmin. At equimolar concentrations of protease and alpha(2)-antiplasmin (5 nM:5 nM) full inhibition of protease activity took place. Monitoring of plasmin activity on an hourly and daily basis revealed a prominent effect of autolysis and decrease of plasmin activity in freshly activated samples. The degree of inhibition as well as plasmin half-life (t(1/2) = 2.48 & PLUSMN; 0.28 days) connected with its degradation was determined.

Automated summary

In this study, the regulatory effects of plasmin and trypsin in the presence of their inhibitor, alpha(2)-antiplasmin, were monitored using the research quartz crystal microbalance (RQCM). The results showed that alpha(2)-antiplasmin could fully inhibit the activity of both proteases. Additionally, it was observed that autolysis and degradation decreased the activity of plasmin in freshly activated samples. The half-life of plasmin was determined to be 2.48 ± 0.28 days.