Lectins, carbohydrate-binding proteins of non-immune origin, that agglutinate cells or precipitate polysaccharides and glycoconjugates, are well distributed in nature, mainly in the Plant Kingdom. The great majority of the plante lectins are present in seed cotyledons where they are found in the cytoplasm or int he protein bodies, although they have also been found in roots, stems and leaves. Due to their peculiar properties, the lectins are used as a tool both for analytical and preparative purposes in biochemistry, cellular biology, immunology and related areas. In agriculture and medicine the use of lectins greatly improved in the last few years. The lextins, with few exceptions, are glycoproteins, need divalent cations to display full activity and are, in general, oligomers with variable molecular weight. Although the studies on lectins have completed a century, their role in nature is yet ynknown . Several hypotheses on their physiological functions have been suggested. Thus, lectins could play important roles in defense against pathogens, plant-microorganism symbiosis, cell organization, embryo morphogenesis, phagocytosis, cell wall elongation, pollen recognition and as reserve proteins. A brief review on the general properties and roles of the lectins is given.

A comparação da metabolização da lectina de Canavalia brasiliensis com as demais proteínas de reservas durante a germinação das sementes na presença de luz foi acompanhada através da combinação de dosagem de proteínas solúveis, determinação da atividade hemaglutinante, cromatografia de afinidade em coluna de Sephadex G-50 e eletroforese em gel de poliacrilamida em presença de dodecilsulfato de sódio (SDS) e 2-mercaptoetanol. Os resultados foram comparados com resultados anteriormente obtidos com sementes germinadas na ausência da luz e ficou evidenciado que, mesmo com as plântuias fotossintetizando, a lectina de Canavalia brasiliensis é preservada, sendo metabolizada após as>demais proteínas de reserva. Estes dados sugerem também que estas proteínas devam ter funções específicas durante o ciclo vital da planta e não se constituem apenas em proteínas de reserva.

Canavalia brasiliensis seed lectin during germination in the presence of light. The mobilization of the lectin of Canavalia brasiliensis during seed germination, in the presence of light, was studied in comparison with the reserve proteins. Methods employed were determination of soluble protein content, hemagglutinating activity, affinity chromatography on Sephadex G-50 column, and PAGE-SDS. The results showed that the lectin was metabolized later than the reserve proteins suggesting that it may have a special function other than a simple reserve protein.

Eletroforese em gel de poliacrilamida das proteínas solúveis extraídas de sementes de doze espécies da tribo Diocleae, apresenta padrão qualitativo semelhante no que diz respeito às bandas correspondentes às lectinas, sugerindo a possibilidade de seu uso como marcadores taxonômicos.

Polyacrylamide gel electrophoresis of the soluble proteins extracted from seeds of twelve species belonging to the tribe Diocleae showed substantive qualitative pattern similiarities between the bands correspondent to the lectins.