Resistance of beta-lactoglobulin-bound lactose to the hydrolysis by beta-galactosidase

An in vitro study was conducted to investigate the sensitivity of lactose-b eta-lactoglobulin conjugates to beta-galactosidase from Kluyveromyces lacti s. The hydrolysis was monitored by ion exchange chromatography. Compared to free lactose or lactulose, which were rapidly hydrolysed, protein-bound la ctose was not hydrolysed by beta-galactosidase even after an extended hydro lysis time. Tryptic digestion of the conjugates before addition of beta-gal actosidase improved the substrate accessibility and led to the release of a bout 50% of the linked lactose. The results strongly suggest that the resis tance of protein bound lactose is linked to the globular and compact struct ure of lactose-beta-lactoglobulin conjugates. (C) 2000 Elsevier Science Ltd . All rights reserved.