Kunitz-type proteinase inhibitors derived by limited proteolysis of the inter-alpha-trypsin inhibitor, VII. Characterization of the bovine inhibitor as double-headed trypsin-elastase inhibitor.

The acid-resistant 14-kDa inhibitor BI-14, released from bovine inter-alpha-trypsin inhibitor, consists of two tandem Kunitz-type domains, and is of a double-headed nature. The Arg-Thr bond connecting both domains was cleaved and the two inhibitory domains were separated. The N-terminal domain is an inhibitor of bovine chymotrypsin and elastases from porcine pancreases and human polymorphonuclear granulocytes, whereas the C-terminal domain interacts with trypsin, plasmin, and chymotrypsin. In the intact inhibitor BI-14 both domains interact independently with the proteinases.