New cell surface bound lectins with complex carbohydrate specificity from members of green algae

Lectins, algal in particular, have immense potential for biomedical applications such as anti-HIV, antitumoral, antimicrobial, anti-inflammatory and antinociceptive activities. In this context, there is a growing interest among researchers on agglutinins from green algae. Here, we have made an attempt to catalogue lectins from various unexplored green algae species. Chlorophyceae members (Chlorella vulgaris, Chlorococcum infusiformis, Desmodesmus dimorphus, D. subspicatus and Scenedesmus quadricauda) were screened for lectin activity using human, pig, sheep, goat and rabbit erythrocytes. All of them showed surface bound lectin activity with highest agglutination titre towards human blood type B erythrocytes and rabbit erythrocytes. Neuraminidase and protease treatment to human blood type B erythrocytes considerably enhanced the agglutination titre of lectins from S. quadricauda, C. vulgaris and D. subspicatus. However, protease treatment of erythrocytes showed no effect on C. infusiformis lectin activity, and decreased the lectin activity of D. dimorphus. Lectins of members of chlorophyceae have shown unique glycoprotein binding specificities as their lectin activity was specifically inhibited by glycoproteins exhibiting complex O-glycans, such as bovine submaxillary mucin, porcine stomach mucin and fetuin. All the algal cultures expressed maximum lectin activity during stationary phase of growth except S. quadricauda which expressed maximum lectin activity during mid-log to stationary phase of cultivation. Possibly, it is a new report on cell surface bound lectins from unexplored members of chlorophyceae for lectin activity.

Lectin activity in mycelial extracts of Fusarium species

ABSTRACT Lectins are non-immunogenic carbohydrate-recognizing proteins that bind to glycoproteins, glycolipids, or polysaccharides with high affinity and exhibit remarkable ability to agglutinate erythrocytes and other cells. In the present study, ten Fusarium species previously not explored for lectins were screened for the presence of lectin activity. Mycelial extracts of F. fujikuroi, F. beomiformii, F. begoniae, F. nisikadoi, F. anthophilum, F. incarnatum, and F. tabacinum manifested agglutination of rabbit erythrocytes. Neuraminidase treatment of rabbit erythrocytes increased lectin titers of F. nisikadoi and F. tabacinum extracts, whereas the protease treatment resulted in a significant decline in agglutination by most of the lectins. Results of hapten inhibition studies demonstrated unique carbohydrate specificity of Fusarium lectins toward O-acetyl sialic acids. Activity of the majority of Fusarium lectins exhibited binding affinity to D-ribose, L-fucose, D-glucose, L-arabinose, D-mannitol, D-galactosamine hydrochloride, D-galacturonic acid, N-acetyl-d-galactosamine, N-acetyl-neuraminic acid, 2-deoxy-D-ribose, fetuin, asialofetuin, and bovine submaxillary mucin. Melibiose and N-glycolyl neuraminic acid did not inhibit the activity of any of the Fusarium lectins. Mycelial extracts of F. begoniae, F. nisikadoi, F. anthophilum, and F. incarnatum interacted with most of the carbohydrates tested. F. fujikuroi and F. anthophilum extracts displayed strong interaction with starch. The expression of lectin activity as a function of culture age was investigated. Most species displayed lectin activity on the 7th day of cultivation, and it varied with progressing of culture age.