Kunitz-Type Proteinase Inhibitors Derived by Limited Proteolysis of the Inter-α-Trypsin Inhibitor, II. Characterization of a Second Inhibitory Inactive Domain by Amino Acid Sequence Determination

Abstract

A short digestion with excess of trypsin releases an inhibitor with an apparent molecular weight of 14,000 from both the inter-alpha-trypsin inhibitor and the ITI-related acid-stable inhibitor. The amino acid sequence of this inhibitor was determined. The inhibitor is composed of two covalently linked homologous Kunitz-type domains. One domain has antitryptic activity, as reported. This paper characterizes the second, inactive domain as also of the Kunitz type.