Comparative Biochemistry and Physiology Part B 127 (2000) 243 – 250 Chemical characterization of the lectin from the freshwater prawn Macrobrachium rosenbergii (De Man) by MALDI-TOF Roberto Zenteno a, *, Lorena Vazquez b , Claudia Sierra b , Ali Pereyra a , Marie Christine Slomianny c , Stephane Bouquelet c , Edgar Zenteno d a Departamento de Bioquı ´mica, Instituto Nacional de Enfermedades Respiratorias, Calzada de Tlalpan 4502, 01040 Mexico b Laboratorio de Lectinas, CIQ, Uniersidad Auto ´noma del Estado de Morelos, Cuernaaca Morelos, 62210 Mexico c Laboratoire de Chimie Biologique, Uniersite ´ des Sciences et Technologies de Lille, UMR du CNRS n o 8576, Villeneued’Ascq, 59655 Cedex, France d Departamento de Bioquı ´mica, Laboratorio de Inmunologı ´a, Facultad de Medicina, UNAM, P.O. Box 70159, 04510 Mexico City, Mexico Received 24 March 2000; received in revised form 25 June 2000; accepted 26 June 2000 Abstract The serum of the freshwater prawn contains a sialic acid specific lectin (MrL) that agglutinates erythrocytes from rat and rabbit, as well as some Gram negative and positive bacterial strains. In this work, we performed the chemical characterization of the MrL purified by affinity chromatography on stroma from rat erythrocytes and by ion exchange chromatography. In its active form, MRL is a dimeric glycoprotein with 9.5 kDa per subunit. The amino acid sequence of the lectin was deduced from peptides obtained after trypsin treatment by matrix-assisted laser desorption ionization mass spectrometry-time of flight analysis (MALDI-TOF). The predicted amino acid sequence of the lectin showed 54% homology with the hyperglycemic hormone from Macrobrachium rosenbergii. It also showed homology with the variable region of the human immunoglobulin  (22%) and  (27%) light chains. The lectin is a glycoprotein with 11% (w/w) carbohydrate content and is constituted by Gal, Man, GlcNAc, GalNAc and NeuAc in a molar ratio of 4:3:2:1:0.6. The primary structure of the carbohydrate chains of the lectin from the freshwater prawn was determined by affinity chromatography of MrL-glycopeptides on Con A and LCA lectin columns, which indicated that the main carbohydrate chains conforming the lectin are N-glycosidically linked. Man 3 GlcNAc 2.1 oligosaccharides were the most abundant structures with 57% followed by Gal 1.3 Man 3 GlcNAc 2.8 with 24%. Our results suggest that the freshwater prawn possess a lectin in the hemolymph plasma, related to those from the immunoglobulin superfamily. © 2000 Elsevier Science Inc. All rights reserved. Keywords: Sialic acid specific lectin; Glycoprotein; MALDI-TOF; Animal lectin; Crustacean; Macrobrachium rosenbergii ; Hyper- glycemic hormone; Immunoglobulin superfamily proteins www.elsevier.com/locate/cbpb 1. Introduction Invertebrate animals lack adaptive immune sys- tems, but they have developed various defense systems that recognize antigens on the surface of * Corresponding author. Tel.: +52-5-6232169; fax: +52-5- 6162419. E-mail address: ezenteno@servidor.unam.mx (R. Zenteno). 0305-0491/00/$ - see front matter © 2000 Elsevier Science Inc. All rights reserved. PII:S0305-0491(00)00260-1