New mannose - specific lectins from garlic ( AZZium sativum ) and ramsons ( AZ & m ursinum ) bulbs *

Two new mannose-binding lectins were isolated from garlic (Allium satiuum, ASA) and ramsons (All&m ursinum, AUA) bulbs, of the family Alliaceae, by affinity chromatography on immobilized mannose. The carbohydrate-binding specificity of these two lectins was studied by quantitative precipitation and hapten-inhibition assay. ASA reacted strongly with a synthetic linear (1 --$ 3)a-o-mannan and S. cerevisiae mannan, weakly with a synthetic (1 + 6)-o-D-mannan, and failed to precipitate with galactomannans from T. gropengiesseri and T. lactis-condensi, a linear mannopentaose, and murine IgM. On the other hand, AUA gave a strong reaction of precipitation with murine IgM, and good reactions with S. cerevisiae mannan and both synthetic linear mannans, suggesting that the two lectins have somewhat different binding specificities for n-o-mannosyl units. Of the saccharides tested as inhibitors of precipitation, those with (Y-(1 + 3)-linked mannosyl units were the best inhibitors of ASA, the a-(1 j 2)-, o-(1 * 4), and o-(1 + 6)-linked mannobioses and biosides having less than one eighth the affinity of the o-(1 + 3)linked compounds. The N-terminal amino acid sequence of ASA exhibits 79% homology with that of AUA, and moderately high homology (53%) with that of snowdrop bulb lectin, also an a-o-mannosyl-binding lectin.