Characterization and Proteolytic origins of specific peptides appearing during lipopolysaccharide experimental mastitis

Abstract

Based on the compositional change of the proteose peptone fraction, proteolysis was studied over time following lipopolys accharide-induced experimental mastitis. Electrophoresis of the proteose peptone fraction revealed many degradation products. Five peptides were identified by amino-terminal sequencing as internal fragments of β-, κ-, αs1-, and αS2-casein that were generated by somatic cell proteases. Although κ-casein is considered particularly resistant to endogenous proteolysis, a κ-casein peptide was electrophoretically isolated in association with a β-casein fragment. The in vitro kinetic studies of casemate hydrolysis by elastase, one of the main polymorphonuclear neutrophil (PMN) proteases, suggested that the β-casein peptide might be generated by elastase. In addition, elastase activity in milk PMN was higher during the inflammation of the mammary gland than prior to infusion.