Glycoconjugate Journal (1992) 9:204-208 Specificity of Amaranthus leucocarpus lectin EDGAR ZENTENO 1., RICARDO LASCURAIN 2, LUIS F. MONTAI~IO 3, LORENA VAZQUEZ 1, HENRI DEBRAY 4 and JEAN MONTREUIL 4 XDepartamento Biologla Experimental, Universidad Aut6noma del Estado de Morelos, Cuernavaca, Morelos, Mexico 2Departamento Bioqulmica, Facultad de Medicina, UNAM, Mexico 04510 D.F. aDepartamento Biologla, lnstituto National de Cardiologia, Mexico 14000 D.F. 4Laboratoire de Chimie Biologique (Unitd mixte du CNRS No 111), Universitd des Sciences et Techniques de Lille Flandres-Artois, 59655 Villeneuve d'Ascq Cedex, France Received 11 December 1991 and revised 28 February 1992 We have demonstrated that Amaranthus leucocarpus lectin hemagglutinating activity was powerfully inhibited by the T-antigen, containing Gal(fll-3)GalNAc(el-3)Ser/Thr, and the Tn-antigen, which contains GalNAc(el-3)Ser/Thr. This suggests that the aeetamido group at C-2 and the axial -OH at C-4 of the N-acetyl-D-galactopyranosylamine ring are important for lectin binding. The hemagglutination assays also established that desialylated and Pronase-treated human type O erythrocytes with an M phenotype were better recognized than erythrocytes from all other blood groups. The recognition was dependent on pH and ionic strength. Keywords: plant lectin, Amaranthus leucocarpus, T and Tn antigen-specific lectin Amaranthus leucocarpus is a Mexican species of the Amaranthus genus with a high nutritional value due to its protein content and the considerable proportion of essential amino acids it possesses [1]. Previous reports have shown similarities between the lectins isolated from A. caudatus [2, 3], A. cruentus [4, 5] and A. leucocarpus [6], such as two 33,000-36,000 Da monomer units forming a native 66,000 Da homodimer, presence of common epitopes and inhibition of their hemagglutinating activity by N-acetyl-D-galactosamine and fetuin, a glycoprotein containing both O- and N-glycosidically linked glycans I-7]. Similarly to A. leucocarpus, the Gal(fl 1-3)GalNAc specificity of A. caudatus lectin has only recently been determined [3]; however, A. leucocarpus induces immunosuppression in animals and is mitogenic for murine spleen lymphocytes [6, 8] where A. caudatus does not exert any such effect [23. In order to identify the nature of these discrepancies, we tried to establish (a) the fine sugar specificity of the A. leucocarpus lectin, and (b) whether human erythrocytes with phenotypes in which N-acetylgalactosamine residues represent important determinants were specifically agglutinated by the leetin. * To whom correspondenceshould be sent at Departamento Bioquimica, Facultad de Medicina, UNAM, PO Box 70-159, Mexico04510 D.F. 0282-0080 © 1992 Chapman & Hall Materials and methods Materials Amaranthus leucocarpus seeds obtained in Tulyehualco (Mexico) were identified at the Centro de Investigaciones Biol6gicas, UAEM, Mexico. The lectin was purified by affinity chromatography on a column containing human type O red blood cell stroma as already described [6]. Ultrogel ACA-202 was from IBF-Biotechnics (Clichy, France); Bio-Gel P-4 and Bio-Gel P-2 were from Bio-Rad (Vitry sur Seine, France). Mucine from bovine submaxillary gland, mucin grade II from porcine stomach, fetuin from fetal calf serum, human ~l-acid glycoprotein, Pronase (Streptomyces griseus, Sigma fraction XXV), neuraminidase (Vibrio cholerae, Sigma fraction V, EC 3.2.1.18) as well as other sugars, chemicals and proteins were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Human serum IgA as well as its O-glycans that contain Gal(fll-3)GalNAc [93 were gifts from Professor G. Spik; ~(2-3)- and c~(2-6)-sialyllactose as well as ovine submaxillary muein were a gift from Dr, G. Strecker (Universit6 des Sciences et Techniques de Lille Flandres-Artois, France). Analytical methods Protein concentration was determined by the method of Lowry et al. [10] using bovine serum albumin as a standard.