Preparation of maltosyl, beta‐cyclodextrinyl, glucosaminyl, and glucosamineoctaosyl derivatives of beta‐lactoglobulin

Abstract

beta‐Lactoglobulin was modified to various degrees with maltose or beta‐cyclodextrin using the cyclic carbonate method and with glucosamine or glucosamineoctaose using the carbodiimide method. Up to 65% of the amino or the carboxyl groups of b‐LG were glycosylated using the two methods, respectively. Up to 32 maltose residues were coupled to b‐LG using the cyclic carbonate method while up to 16.6 glucosamine residues were coupled to b‐LG using the carbodiimide method. This resulted because more than one disaccharide was attached to each group of b‐LG that was modified. Even so, the coupling efficiency of the active compound was higher for the carbodiimide derivative than for the cyclic carbonate derivative. The electrophoretic analyses of the glycosylated proteins indicated that a heterogeneous population of protein molecules was formed during modification. The electrophoretic mobility of maltosyl‐beta‐lactoglobulin derivatives was essentially unchanged while the mobility of glucosaminyl‐beta‐lactoglobulin derivatives decreased as the extent of modification increased. The glycosylated proteins were suitable for studying their structural and functional properties.