Physicochemical comparison of goat β-lactoglobulin with the bovine varieties

Abstract

β-Lactoglobulin was prepared from mixed goat milk and multiple amino acid analyses were carried out. One difference in basic residues was found from the analysis previously reported. Ultracentrifugal, light-scattering, and optical rotatory dispersion experiments showed that the goat protein is quite similar to the bovine β-lactoglobulins in most of its physical properties, but indications were obtained that it is conformationally less stable at low pH values than its bovine analog. Titration experiments indicate that six of the free carboxylic acid (Asp and Glu) residues in monomeric bovine β-lactoglobulin B do not occur in titratable form in the caprid β-lactoglobulin. These experiments also indicate a low pH-induced conformational change to a molecule of slightly greater radius.