Susceptibility of equine kappa- and beta-caseins to hydrolysis by chymosin

Equine whole casein was hydrolysed by chymosin and some peptides generated were characterised by microsequencing after reversed-phase high performance liquid chromatography or sodium dodecyl sulphate polyacrylamide gel electrophoresis. beta-Casein was readily hydrolysed into amino- and carboxy-terminal fragments after cleavage of the Leu(190)-Tyr(191) bond. These two fragments seemed to be resistant to further chymosin hydrolysis on incubation for up to 24h. Equine kappa-casein was purified by affinity chromatography on immobilised wheat germ agglutinin. O-Glycosylated kappa-casein was found to represent less than 6.8% of the equine casein components. Equine kappa-casein was also hydrolysed and para-kappa-casein and glycomacropeptide were generated after cleavage of the Phe(97)-Ile(98) bond. (C) 2002 Elsevier Science Ltd. All rights reserved.