Binding specificities of inulin-binding immunoglobulins for sinistrin and oligosaccharides isolated from asparagus roots.

The major aim of this study was to further investigate the fine specificity of myeloma proteins recognizing epitopes on fructans. Our studies showed that UPC 61, EPC 109, and a hybrid antibody composed of the heavy chain from UPC 61 and the light chain from EPC 109, UPC 61H:EPC 109L, not only bind to inulin which is a linear fructan of beta (2----1) fructofuranosyl linkages, but also bind to sinistrin, a branched molecule consisting of a beta (2----1) fructofuranosyl backbone with beta (2----6) branch points. The fine binding specificity of these three antibodies for the beta (2----1) fructofuranosyl linkages found in inulin-BSA can be further studied by their binding to fructan oligosaccharides isolated from asparagus roots. From a comparative analysis of the amino acid sequences and the apparent affinity constants (aKa) of UPC 61, EPC 109, and the hybrid for various fructan oligosaccharides, it appears that the light chain of the immunoglobulin molecule makes an important contribution to the binding specificity. Finally we report for the first time that a monoclonal antibody specific for beta (2----6) fructans can also bind specifically to inulin-BSA with a lower affinity. This antibody derives its VH and VL from the VHX24 and Vk10b gene families, respectively, which are different from the gene families utilized by UPC 61 and EPC 109 (VHJ606 and Vk11 gene families).