Isolation and characterization of a lectin from the fruit of Clerodendron trichotomum

An agglutinin of Clerodendron trichotomum fruit (CTA), found to be specific for N-acetyl-D-galactosamine and D-galactose, was isolated and characterized. The fruit extract was decolorized first by passage through a Toyopearl column and a phenyl-Sepharose column. Then the lectin activity was adsorbed on p-aminophenyl N-acetyl-alpha-D-galactosaminide- or p-aminophenyl beta-D-galactoside-Sepharose, and eluted as a sharp peak with 0.2 M lactose. The purified CTA was found to be homogeneous by SDS-polyacrylamide gel electrophoresis, gel chromatography and ultracentrifugal analysis, and was determined to be a glycoprotein homodimer with a molecular weight of 56,000 daltons. Hemagglutination-inhibition assay indicated that CTA is most specific for N-acetyl-D-galactosaminide with a hydrophobic aglycon.