Anti-galactan activity in Tridacna maxima (Röding) haemolymph. Calcium dependence of the haemagglutinins and precipitins.

A powerful natural agglutinin with haemagglutinating and precipitating properties has been found in the haemolymph from the elongate clam Tridacna maxima (Röding). The agglutinin shows anti-galactan properties and reacts with a variety of bacteria-, plant-, invertebrate- and vertebrate-derived galactans, glycopeptides and polysaccharides. Previous studies which showed that the agglutinin-combining sites were inhibited by 2-acetamido-2-deoxy-D-galactose and D-galactose also revealed some anomalies in the reactions of the agglutinin with different saccharide-containing macromolecules. In an attempt to resolve these anomalies, the present study further examines the precipitating and haemagglutinating properties of the agglutinin and illustrates a requirement of the agglutinin for Ca2+. The ability of the T. maxima agglutinin to precipitate with structures containing terminal beta-linked 2-acetamido-2-deoxy-D-galactopyranosyl or D-galactopyranosyl groups suggests that the Tridacna haemolymph and purified lectin will find considerable application in the study of many biologically important carbohydrates.