Physical characterization of ovoinhibitor, a trypsin and chymotrypsin inhibitor from chicken egg white

A simple method for preparing ovoinhibitor of high specific activity from commercially available chicken ovomucoid is presented. Ultracentrifuge and light-scattering measurements on ovoinhibitor give a weight average molecular weight of 46,500. This, with inhibition data for trypsin and chymotrypsin, indicates an inhibitor to enzyme combining molar ratio of 1:2. Amino acid and chemical analyses of chicken ovoinhibitor show some differences from chicken and turkey ovomucoids, but these do not clearly account for the enzymic differences. Enzymic studies confirm that ovoinhibitor, like turkey ovomucoid but unlike chicken ovomucoid, inhibits trypsin and chymotrypsin, the inhibition of one enzyme being essentially unaffected by the presence of the other.