Reaction of a tumour-associated trypsin inhibitor with serine proteinases associated with coagulation and tumour invasion.

The inhibition of six serine proteinases by a tumour-associated trypsin inhibitor (TATI) was studied using synthetic peptide substrates. Physiological concentrations of TATI inhibited the amidolytic activities of trypsin, plasmin, urokinase and tissue plasminogen activator (tPA). Chymotrypsin, kallikrein and thrombin were also inhibited, but by much higher concentrations of TATI. The ability of TATI to inhibit trypsin, plasmin, urokinase and tPA suggests that it has a role in proteolytic processes in vivo involving these enzymes.