Fetuin as a trypsin inhibitor

Fetuin per se is a moderately strong trypsin inhibitor of the temporary type and retains its antitryptic activity upon desialicization. It forms a reversible 1:1 complex with β-trypsin and is functionally homogeneous in this respect. Complex formation is an entropy-driven reaction evidently due to release of structured water associated with the individual proteins. It is concluded that the contact area in the complex probably includes the active site of trypsin and that dissociation of the complex is rapid.