Structural differences between trypsin-inhibitors isolated from Cucurbitaceae family seeds: immunological, NMR and CD studies.

By manifold immunizations of rabbits with virgin or modified trypsin inhibitor III from squash seeds and trypsin inhibitor II b from cucumber seeds, specific antibodies were produced. In double immunodiffusion the anti-squash inhibitor antibody also gave weak precipitate arcs with inhibitor I from squash, inhibitor II from summer squash and with inhibitor I from zucchini, but not with inhibitor II b from cucumber seeds. The genus of Cucurbita trypsin inhibitors, preincubated with the antibody, lost their antitrypsin activity. The antibody showed a significantly weaker effect on the activity of the inhibitor from cucumber sees. 1H-NMR and CD spectra also confirm structural differences between trypsin inhibitors from the genus of Cucurbita and the cucumber (genus of Cucumis) inhibitor.