Immunochemical studies on the combining sites of bovine immunoglobulins reactive with invertase.

Calcium-dependent and -independent bovine IgG reactive with invertase were isolated by affinity chromatography on invertase-coupled Sepharose 4B and their specificities were determined by competitive binding assays. The binding of 125I-labeled calcium-dependent and -independent bovine IgG reactive with invertase to invertase-coupled Sepharose 4B were most effectively inhibited by invertase and mannan. The binding was more weakly inhibited by mannose, glucose, and methyl alpha-D-mannopyranoside, whereas that was much more weakly inhibited by other monosaccharides and glycoproteins. These findings suggest that the combining sites of calcium-dependent and -independent bovine IgG reactive with invertase may be specific for invertase and/or mannan.