New lymphocyte stimulating monocot lectins from family Araceae. II.

Two lectins purified from the tubers of Arisaema consanguineum Schott (ACA) and A. curvatum Kunth (ACmA) belonging to the monocot family Araceae were mitogenic for human peripheral blood mononuclear cells (PBMC) in the [3H]-thymidine uptake assay. ACA and ACmA had an optimum stimulatory concentration of 10-25 micrograms/ml and 50-100 micrograms/ml, respectively, as observed in PBMC from five different individuals. The mitogenic response of PBMC was inhibitable in a dose-dependent manner by asialofetuin. The lectins were T-cell specific, and stimulation kinetic studies using ACA and ACmA showed that they induce maximum thymidine uptake in PBMC at day 4 and 3, respectively.

Purification and properties of four monocot lectins from the family Araceae.

Four new monocot lectins from the tubers of araceous plants, namely, Arisaema consanguineum Schott (ACA), A. curvatum Kunth (ACmA) and Sauromatum guttatum Schott (SGA) from the tribe Areae, and Gonatanthus pumilus D. Don (GPA) from the tribe Colocasieae have been purified by affinity chromatography on asialofetuin-linked amino activated silica beads. These lectins possess similar physicochemical and biological properties. All the lectins gave a single peak on HPLC size exclusion and cation exchange columns, and a single band on PAGE, (pH 4.5). In SDS-PAGE, all the lectins gave a single band corresponding to a subunit of M(r) 1,3000. All the lectins yielded multiple peaks on anion-exchange column, multiple bands on non-denatured PAGE (pH 8.3) and a family of bands on isoelectric focusing. The lectins agglutinate rabbit, rat and sheep red blood cells (RBCs) but are inactive towards human ABO erythrocytes. The haemagglutination activity of these lectins is inhibited by asialofetuin only, while simple sugars/derivatives including chitin, porcine mucin and fetuin did not react. In serological studies against rabbit anti-SGA serum, all four lectins produced immunoprecipitin lines. The lectins within each tribe were identical but the lectins belonging to the tribe Areae were only partially identical to the lectins from the tribe Colocasieae.

New lymphocyte stimulating monocot lectins from family Araceae.

Three monocot lectins from underground tubers of plants belonging to the family Araceae were investigated for their mitogenic potential towards human peripheral blood lymphocytes. All the three lectins turned out to be potent mitogens in the [3H]-thymidine uptake assay. Gonatanthus pumilus lectin was mitogenic at an optimum concentration of 25 micrograms/ml while Alocasia indica and Sauromatum guttatum lectins were most effective at a concentration of 50 micrograms/ml. [3H]-thymidine incorporation studies further revealed that the lectins were T-cell mitogens and did not induce any appreciable DNA synthesis in B-enriched lymphocytes. The proliferation kinetic studies detected maximum incorporation on day 3 and the mitogenic response was shown to be inhibited by asialofetuin in a concentration-dependent manner.

Amaranthus hypochondriacus and A. tricolor lectins: isolation and characterization.

Asialofetuin-linked amino activated silica was used for the affinity purification of lectins from Amaranthus hypochondriacus Linn (AHL) and A. tricolor Linn (ATL). Like a few other Amaranthus lectins, these lectins were also inhibited by N-acetyl-D-galactosamine, fetuin and asialofetuin; they agglutinated human and different animal erythrocytes. The purified lectins yielded a single band on PAGE pH 8.3, pH 4.5 and SDS-PAGE, pH 8.3. These also gave a single peak in gel exclusion on Biogel P-200, HPLC 300 SW and cation exchange columns. However, both lectins gave multiple peaks in anion exchange column and multiple bands in isoelectric focusing. AHL and ATL are dimeric proteins in which the subunits having M(r) 29,000 and 39,000, respectively, are not held together by disulphide linkages. The pure lectins are glycoproteins and do not require Ca2+, Mn2+ and Mg2+ for their agglutination activity.

Occurrence and characterization of lectins in actinomycetes.

25 species of actinomycetes were tested for the occurrence of lectins. Using a battery of normal and desialized erythrocytes, each species was screened for 3 types of lectin activity i.e. surface bound, extracellular and intracellular. As many as 13 species showed one or more types of activity; some of them were characterized with regard to their biological action spectrum and sugar specificity.

Occurrence and characterization of lympho-agglutinins in Indian plants.

Lympho-agglutinins have been detected and characterized in 31 plant species. Out of these, 14 agglutinated only the neuraminidase-treated cells. The lectin-rich genera included Crotalaria and Erythrina (Fabaceae), Amaranthus (Amaranthaceae), Artocarpus (Moraceae) and Clerodendron (Verbenaceae). The new lectins varied in their potency and biological action spectra. The 3 Artocarpus species were found to be exceptionally potent and specific for melibiose, an alpha-D-galactoside. Among the most effective sugar inhibitors for other lectins were N-acetyl-galactosamine, lactose, galactose and asialofetuin/fetuin.

Occurrence and characterization of lympho-agglutinins in Indian plants.

A survey of the occurrence of lympho-agglutinins was carried out on seeds of 150 species of wild and cultivated plants. Potent agglutinins were detected in 17 extracts by employing lymphocytes of man, guinea pig, goat and sheep in the bioassay. Except for one species each of Mimosoideae, Euphorbiaceae and Clusiaceae, all the agglutinins were found in fabaceous seeds. Two of the agglutinins, namely, Parkia biglandulosa and Erythrina arborescens, were found to be monospecific for guinea pig and human lymphocytes, respectively, while the others agglutinated lymphocytes of 2-4 different species. The agglutination inhibition tests revealed the predominance of galactose (or its derivatives) binding lectins over those specific for glucose-mannose series.