HYDROLYSIS OF BOVINE BETA-LACTOGLOBULIN BY VARIOUS PROTEASES AND IDENTIFICATION OF SELECTED PEPTIDES

beta-Lactoglobulin (beta-Lg) was incubated with a number of proteases to seek conditions under which relatively large fragments were produce d in good yield. The proteases used were bromelain, papain, pepsin, tr ypsin, endoproteinase Arg-C, aminopeptidase and carboxypeptidase Y. Br omelain-catalysed hydrolysis led to rapid hydrolysis of beta-Lg and th e formation of a large number of small peptides. Pepsin hydrolysed onl y a fraction of the beta-Lg molecules, and the few released fragments were degraded into small peptides. Both papain and trypsin degraded be ta-Lg with the formation of medium-sized peptides (1-5 kDa), of which seven were identified. Endoproteinase Arg-C did not hydrolyse native b eta-Lg, whereas heat-treated beta-Lg was degraded and six peptides wit h molecular masses around 2 kDa were identified. None of the exopeptid ases catalysed complete removal of a substantial part of beta-Lg. A fe w conditions under which relatively large and easily purifiable fragme nts were produced from beta-Lg were identified. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.