Cuatrecasas P, Tell G P
Proc Natl Acad Sci U S A. 1973 Feb;70(2):485-9. doi: 10.1073/pnas.70.2.485.
Concanavalin A and wheat germ agglutinin are as effective as insulin in enhancing the rate of glucose transport and in inhibiting epinephrine-stimulated lipolysis in isolated adipocytes. These lectins, also like insulin, inhibit basal as well as epinephrine-stimulated adenylate cyclase activity of membranes obtained from homogenates of fat cells. Low concentrations of wheat germ agglutinin enhance the specific binding of insulin to receptors of fat cells and liver membranes. Higher concentrations of this plant lectin, as well as of concanavalin A, competitively displace the binding of insulin to receptors in these tissues. These effects are equally apparent in insulin-binding proteins solubilized from membranes, indicating that the plant lectins interact directly with insulin receptors. All of the effects observed with the plant lectins are reversed by simple sugars that bind specifically to these plant proteins. Agarose derivatives of the plant lectins effectively adsorb solubilized insulin-binding proteins, and these can be eluted with buffers containing specific simple sugars. The possible implications of these findings to certain biological properties (mitogenicity) of these lectins and to the mechanism of action of other growth-promoting substances are considered.
刀豆球蛋白A和麦胚凝集素在提高葡萄糖转运速率以及抑制分离的脂肪细胞中肾上腺素刺激的脂肪分解方面与胰岛素同样有效。这些凝集素也像胰岛素一样，抑制从脂肪细胞匀浆获得的膜的基础以及肾上腺素刺激的腺苷酸环化酶活性。低浓度的麦胚凝集素增强胰岛素与脂肪细胞和肝细胞膜受体的特异性结合。较高浓度的这种植物凝集素以及刀豆球蛋白A竞争性地取代胰岛素与这些组织中受体的结合。这些作用在从膜中溶解的胰岛素结合蛋白中同样明显，表明植物凝集素直接与胰岛素受体相互作用。用与这些植物蛋白特异性结合的单糖可逆转植物凝集素观察到的所有作用。植物凝集素的琼脂糖衍生物有效地吸附溶解的胰岛素结合蛋白，并且这些蛋白可用含有特定单糖的缓冲液洗脱。考虑了这些发现对这些凝集素的某些生物学特性（促有丝分裂性）以及其他生长促进物质作用机制的可能影响。
