A study of plant lectins and antifungal proteins with emphasis on those of leguminous origin

Defense proteins are produced by a wide range of organisms including mammals, insects, plants, fungi and bacteria. In this study, focus was placed on 2 kinds of defense proteins in plants, namely, lectins/hemagglutinins and defensin-like peptides/defensins. Three lectins, one hemagglutinin (i.e. lectin whose hemagglutinating activity cannot be inhibited by simple saccharides), one defensin and two defensin-like peptides were isolated from 5 species of plants. The isolation procedure included different chromatographic techniques, involving ion exchange chromatography, affinity chromatography and gel filtration.;A heterodimeric 60 kDa lectin was isolated from the ground bean ( Vigna sesquipedalis cv ground bean). Its hemagglutinating activity was inhibited by polygalacturonic acid and not by galacturonic acid and other simple monosaccharides. Ground bean lectin exhibited mitogenic activity on murine splenocytes, reduced the viability of hepatoma and leukemia cells, and exerted an inhibitory activity toward HIV-1 reverse transcriptase.;A homotetrameric 120-kDa agglutinin was isolated from haricot bean seeds. It manifested a weaker mitogenic activity than concanavalin A toward mouse splenocytes and exhibited antiproliferative activity toward several tumor cell lines.;A homodimeric 60-kDa lectin with specificity toward mannose, glucose and rhamnose and substantial N-terminal sequence to Concanavalin A has been isolated from Canavalia gladiata legumes. In contrast to Con A, the mitogenic activity of knife bean lectin toward mouse splenocytes but not its antiproliferative activity toward tumor cells could be abrogated by 200 mM glucose. The lectin inhibited HIV-1 reverse transcriptase, but did not exhibit antifungal activity.;A homodimeric 30-kDa glucose/mannose-specific lectin was purified from emperor banana. In contrast to Con A, the mitogenic activity of emperor banana lectin (EBL) toward mouse splenocytes but not its NO stimulatory effect toward mouse macrophages could be abrogated by 200 mM glucose. It also inhibited proliferation of tumor cells and inhibited HIV-1 reverse transcriptase.;A plant defensin-like peptide, with a molecular mass around 6-kDa, was purified from the seeds of Chinese lima beans (Phaseolus lunatus L. ). Phld exerted an antifungal activity and an antibacterial action. Phld could reduce the activity of HIV-1 reverse transcriptase and inhibit translation in a cell-free rabbit reticulocyte lysate system. (Abstract shortened by UMI.)...