CHARACTERIZATION OF A NATURAL HEMAGGLUTININ WITH AFFINITY FOR ACETYLATED AMINOSUGARS IN THE SERUM OF THE MARINE PRAWN, PENAEUS-INDICUS (EDWARDS,H.MILNE)

A natural haemagglutinin was detected in the serum of the marine prawn Penaeus indicus, using mammalian erythrocytes (RBC). The haemagglutin ation profile and cross-adsorption tests revealed a strong reactivity with human A RBC, and trypsinisation of this RBC type enhanced their s usceptibility for agglutination by the serum. The agglutinating activi ty did not require Ca2+ or Mg2+, was insensitive to EDTA and EGTA, sta ble in a wide pH range (pH 3 to 9) and labile at or above 80 degrees C . Ammonium sulphate and trichloroacetic acid completely precipitated t he haemagglutinating activity from serum, suggesting it is a protein o r glycoprotein. However, neither trypsin treatment nor periodate oxida tion of serum abrogated the agglutinating activity. Haemagglutination- inhibition assays performed with several carbohydrates and glycoprotei ns revealed a unique specificity of serum agglutinin for acetylated am inosugars and that the presence of the acetyl group was essential for agglutinin-ligand interaction. The haemagglutinating activity of the s erum could be specifically inhibited by lipopolysaccharide from Salmon ella abortus equi, but not with lipopolysaccharide from five other bac terial species. (C) 1997 Academic Press Limited.