Occurrence of highly yielded lectins homologous within the genus Eucheuma

We previously reported that the red alga Eucheuma serra contains large amou nts of mitogenic isolectins (ESA-1 and ESA-2), the hemagglutinating activit ies of which were strongly inhibited by glycoproteins bearing high mannose- type N-glycans. We therefore further examined two other species, E. amakusa ensis and E. cottonii. Several lectins were isolated easily by a combinatio n of extraction with aqueous ethanol, precipitation with cold ethanol, gel filtration, and ion exchange chromatography from both species, respectively . The purified lectins were designated as EAA-1, EAA-2, EAA-3, ECA-1 and EC A-2 after the specific names of both algae. The yields of EAAs and ECAs wer e as high as 2.8 and 2.7 mg g(-1) of dry tissue, respectively, indicating t hat both species would also be good sources for high lectin yields. The fiv e purified lectins shared the same properties in hemagglutinating activity, mitogenic activity, and hemagglutination-inhibition test in which glycopro teins bearing high mannose-type N-glycans were the most inhibitory. They al so had almost identical molecular weight and 20 N-terminal amino acid seque nce to each other and to those of ESAs, and only differed in the isoelectri c point, indicating that they are isolectins to each other. The study thus demonstrated that several species of Eucheuma contain high yields of lectin s homologous between species, suggesting that the genus as a whole may be c onsidered as a valuable source of lectin proteins.